Index: ActiviteitenOpvolging/ActiviteitenOpvolging/ActiviteitenOpvolgingForm.vb
===================================================================
diff -u -r1727 -r1735
--- ActiviteitenOpvolging/ActiviteitenOpvolging/ActiviteitenOpvolgingForm.vb	(.../ActiviteitenOpvolgingForm.vb)	(revision 1727)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/ActiviteitenOpvolgingForm.vb	(.../ActiviteitenOpvolgingForm.vb)	(revision 1735)
@@ -181,13 +181,17 @@
         _domainController.SelectEmployee(employeeIndex, employee)
         'Send message that the selected employee changed to all user controls.
         _employeeUserControls.ForEach(Sub(employeeUserControl) employeeUserControl.SelectedEmployeeChanged())
+        'Refresh the grids, so one can recolor.
+        RefreshUserGridsData()
     End Sub
 
     ''' <inheritdoc/>
     Public Sub DeselectEmployee(employeeIndex As Integer) Implements IEmployeesMainForm.DeselectEmployee
         _domainController.DeselectEmployee(employeeIndex)
         'Send message that the selected employee changed to all user controls.
         _employeeUserControls.ForEach(Sub(employeeUserControl) employeeUserControl.SelectedEmployeeChanged())
+        'Refresh the grids, so one can recolor.
+        RefreshUserGridsData()
     End Sub
 
     ''' <inheritdoc/>
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/configs/ConfigsLoader.vb
===================================================================
diff -u -r1715 -r1735
--- ActiviteitenOpvolging/ActiviteitenOpvolging/configs/ConfigsLoader.vb	(.../ConfigsLoader.vb)	(revision 1715)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/configs/ConfigsLoader.vb	(.../ConfigsLoader.vb)	(revision 1735)
@@ -266,10 +266,10 @@
             End Get
         End Property
         Public ReadOnly Property AllFinishedActivitiesColor As color
-        Private ReadOnly _colorsUsers As New List(Of Color)
-        Public ReadOnly Property ColorsUsers As List(Of Color)
+        Private ReadOnly _colorsEmployees As New List(Of Color)
+        Public ReadOnly Property ColorsEmployees As List(Of Color)
             Get
-                Return New List(Of Color)(_colorsUsers)
+                Return New List(Of Color)(_colorsEmployees)
             End Get
         End Property
 #End Region
@@ -322,8 +322,8 @@
                         AddColorActivity(identifier, value, False)
                     ElseIf identifier.Equals("ColorActivityAllFinished") Then
                         _AllFinishedActivitiesColor = GetColorFromHexStringValue(value)
-                    ElseIf identifier.Contains("ColorUser") Then
-                        _colorsUsers.Add(GetColorFromHexStringValue(value))
+                    ElseIf identifier.Contains("ColorEmployee") Then
+                        _colorsEmployees.Add(GetColorFromHexStringValue(value))
                     Else
                         Throw New Exception($"Unknown configuration: '{line}'.")
                     End If
@@ -447,8 +447,8 @@
             End If
 
             'Colors users.
-            If _colorsUsers.Count < NumberOfEmployees Then
-                Throw New ConfigurationException($"The colors for the users are not defined or are fewer than the amount of users {NumberOfEmployees}.")
+            If _colorsEmployees.Count < NumberOfEmployees Then
+                Throw New ConfigurationException($"The colors for the employees are not defined or are fewer than the amount of users {NumberOfEmployees}.")
             End If
         End Sub
 
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityStoppedState.vb
===================================================================
diff -u -r1734 -r1735
--- ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityStoppedState.vb	(.../ActivityStoppedState.vb)	(revision 1734)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityStoppedState.vb	(.../ActivityStoppedState.vb)	(revision 1735)
@@ -1,18 +1,16 @@
 Public Class ActivityStoppedState
     inherits ActivityState
 
-    Private ReadOnly _employee As IEmployee
-
     'Not from other state.
     Public Sub New(activity As IActivity, employee As IEmployee)
         Me.Activity = activity
-        _employee = employee
+        CurrentEmployee = employee
     End Sub
 
     'From other state.
     Public Sub New(state As ActivityState)
         Activity = state.Activity
-        _employee = state.GetEmployee()
+        CurrentEmployee = state.GetEmployee()
     End Sub
 
     ''' <inheritdoc/>
@@ -22,7 +20,7 @@
 
     ''' <inheritdoc/>
     Public Overrides Function GetEmployee() As IEmployee
-        Return _employee
+        Return CurrentEmployee
     End Function
 
     ''' <inheritdoc/>
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/domain/managers/implementations/EmployeeManager.vb
===================================================================
diff -u -r1723 -r1735
--- ActiviteitenOpvolging/ActiviteitenOpvolging/domain/managers/implementations/EmployeeManager.vb	(.../EmployeeManager.vb)	(revision 1723)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/domain/managers/implementations/EmployeeManager.vb	(.../EmployeeManager.vb)	(revision 1735)
@@ -68,6 +68,9 @@
             Throw New Exception($"An employee was already chosen for number (index): {employeeNumber}.")
         End If
 
+        'Update the employeeNumber in the employee.
+        employee.Number = employeeNumber
+
         'Add employee to dictionary of selected employees -> set the value according to an employee number.
         _selectedEmployeesDictionary.Item(employeeNumber) = employee
     End Sub
@@ -80,6 +83,10 @@
             'The employee was not selected, thus can't be deselected.
             Throw New Exception("Cannot remove the selection of a non-selected employee.")
         End If
+
+        'Update the employee number of the employee.
+        _selectedEmployeesDictionary.Item(employeeNumber).Number = -1
+
         'Remove the employee -> set the value back to 'Nothing'.
         _selectedEmployeesDictionary.Item(employeeNumber) = Nothing
     End Sub
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/screens/employee/EmployeeUserControl.vb
===================================================================
diff -u -r1727 -r1735
--- ActiviteitenOpvolging/ActiviteitenOpvolging/screens/employee/EmployeeUserControl.vb	(.../EmployeeUserControl.vb)	(revision 1727)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/screens/employee/EmployeeUserControl.vb	(.../EmployeeUserControl.vb)	(revision 1735)
@@ -52,7 +52,7 @@
     ''' </summary>
     Private Sub EmployeeUserControl_Paint(sender As Object, e As PaintEventArgs) Handles Me.Paint
         'Border color.
-        Dim borderColor = ConfigsLoader.ColorsUsers(EmployeeIndex)
+        Dim borderColor = ConfigsLoader.ColorsEmployees(EmployeeIndex)
         'Border thickness.
         Const borderThickness As Integer = 5I
         'Border rectangle.
@@ -71,11 +71,8 @@
         _currentUserControl = userControl
         'Remove the current user control from the screen.
         UserControlPanel.Controls.Clear()
-        'Set the properties of the user control.
-        With userControl
-            'Make it exactly as big as the panel it will go into.
-            .Size = UserControlPanel.Size
-        End With
+        'Make it exactly as big as the panel it will go into.
+        userControl.Size = UserControlPanel.Size
         'Add it onto the panel.
         UserControlPanel.Controls.Add(userControl)
     End Sub
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityStartedState.vb
===================================================================
diff -u -r1734 -r1735
--- ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityStartedState.vb	(.../ActivityStartedState.vb)	(revision 1734)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityStartedState.vb	(.../ActivityStartedState.vb)	(revision 1735)
@@ -1,18 +1,16 @@
 Public Class ActivityStartedState
     Inherits ActivityState
 
-    Private ReadOnly _employee As IEmployee
-
     'Not from other state.
     Public Sub New(activity As IActivity, employee As IEmployee)
         Me.Activity = activity
-        _employee = employee
+        Me.CurrentEmployee = employee
     End Sub
 
     'From other state.
     Public Sub New(state As ActivityState, employee As IEmployee)
         Activity = state.Activity
-        _employee = employee
+        Me.CurrentEmployee = employee
     End Sub
 
     ''' <inheritdoc/>
@@ -22,12 +20,12 @@
 
     ''' <inheritdoc/>
     Public Overrides Function GetEmployee() As IEmployee
-        Return _employee
+        Return CurrentEmployee
     End Function
 
     ''' <inheritdoc/>
     Public Overrides Sub StopActivity(employee As IEmployee)
-        If Not _employee.Equals(employee) Then
+        If Not CurrentEmployee.Equals(employee) Then
             'Different employee.
             Throw New Exception($"A different employee can't stop a started activity. Current activity belongs to {employee.ToString()}")
         End If
@@ -36,7 +34,7 @@
 
     ''' <inheritdoc/>
     Public Overrides Sub FinishActivity(employee As IEmployee)
-        If Not _employee.Equals(employee) Then
+        If Not CurrentEmployee.Equals(employee) Then
             'Different employee.
             Throw New Exception($"A different employee can't finish a started activity. Current activity belongs to {employee.ToString()}")
         End If
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/mappers/CacheMapper.vb
===================================================================
diff -u -r1733 -r1735
--- ActiviteitenOpvolging/ActiviteitenOpvolging/mappers/CacheMapper.vb	(.../CacheMapper.vb)	(revision 1733)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/mappers/CacheMapper.vb	(.../CacheMapper.vb)	(revision 1735)
@@ -172,7 +172,6 @@
                 .Id = ExtractItemFromDataReader(dr, $"ActiviteitID_{i}", String.Empty)
                 .QuantityToProduce = ExtractItemFromDataReader(dr, $"Aantal_{i}", 0)
                 .Label = ExtractItemFromDataReader(dr, $"Label_{i}", String.Empty)
-                .EmployeeInitials = ExtractItemFromDataReader(dr, $"Gebruiker_{i}", String.Empty)
                 .IsReadOnly = ExtractItemFromDataReader(dr, $"ReadOnly_{i}", False)
                 .StartTimeStamp = ExtractItemFromDataReader(dr, $"StartTijdstip_{i}", DateTime.MinValue)
                 'Subtract time when date was specified. Time is gotten from config.
@@ -182,7 +181,8 @@
                 .WorkItem = workItem
 
                 'Fetch the employee if defined.
-                Dim employee As IEmployee = employees.FirstOrDefault(Function(employeeToCheck) employeeToCheck.Initials.Equals(.EmployeeInitials))
+                Dim employeeInitials = ExtractItemFromDataReader(dr, $"Gebruiker_{i}", String.Empty)
+                Dim employee As IEmployee = If(employeeInitials.Equals(string.Empty), Nothing,employees.FirstOrDefault(Function(employeeToCheck) employeeToCheck.Initials.Equals(employeeInitials)))
                 'Set the current state based on the enum value. If the quantity is 0, the status is automatically zero.
                 .State = ConvertEnumValueToActivityState(If(.QuantityToProduce = 0, ActivityStateEnum.Zero, ActivityStateEnumMapper.GetActivityStateFromLetter(ExtractItemFromDataReader(Of Char)(dr, $"Status_{i}"))), activity, employee)
             End With
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/screens/DataGridViewUserControl.vb
===================================================================
diff -u -r1723 -r1735
--- ActiviteitenOpvolging/ActiviteitenOpvolging/screens/DataGridViewUserControl.vb	(.../DataGridViewUserControl.vb)	(revision 1723)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/screens/DataGridViewUserControl.vb	(.../DataGridViewUserControl.vb)	(revision 1735)
@@ -61,7 +61,7 @@
             'Set properties of datagrid view. 
 
             'Background color.
-            WorkItemsDataGridView.BackgroundColor = color.White
+            WorkItemsDataGridView.BackgroundColor = Color.White
 
             'Cell makeup.
             'Center header cells.
@@ -265,7 +265,8 @@
             UpdateActivityCellTimeStatusIndication(activity, cell)
             'Update background color.
             UpdateActivityCellBackground(workItem, activity, cell)
-            'todo Update border based on user
+            'Update border based on employee.
+            UpdateActivityCellBorder(workItem, activity, cell)
         Next
     End Sub
 
@@ -304,7 +305,7 @@
     End Sub
 
     ''' <summary>
-    ''' 
+    ''' Update the background of the cell based on the activity status.
     ''' </summary>
     ''' <param name="activity"></param>
     ''' <param name="dataGridViewCell"></param>
@@ -326,6 +327,26 @@
     End Sub
 
     ''' <summary>
+    ''' Update the border of the cell. Depends on the state and the employee.
+    ''' </summary>
+    ''' <param name="workItem"></param>
+    ''' <param name="activity"></param>
+    ''' <param name="dataGridViewCell"></param>
+    Private Sub UpdateActivityCellBorder(workItem As IWorkItem, activity As IActivity, dataGridViewCell As DataGridViewCell)
+        If activity.Status = ActivityStateEnum.Started AndAlso activity.CurrentEmployee.Number <> -1 Then
+            'The employee is selected for this activity in the started state.
+            'Only this type of cell is supported.
+            If Not TypeOf dataGridViewCell Is BorderedTextFigureCell Then Throw New InternalException($"Only cells of type {TypeName(New BorderedTextFigureCell)} are supported when updating the cell for an activity.")
+
+            'Cast cell as right type.
+            Dim cell As BorderedTextFigureCell = dataGridViewCell
+
+            cell.BorderColor = ConfigsLoader.ColorsEmployees(activity.CurrentEmployee.Number)
+            cell.BorderThickness = 3 'todo Configureerbaar maken
+        End If
+    End Sub
+
+    ''' <summary>
     ''' Disable the selection changed event, useful for ignoring triggers by adding new rows.
     ''' </summary>
     Private _skipSelectionChanged = False
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityFinishedState.vb
===================================================================
diff -u -r1730 -r1735
--- ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityFinishedState.vb	(.../ActivityFinishedState.vb)	(revision 1730)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityFinishedState.vb	(.../ActivityFinishedState.vb)	(revision 1735)
@@ -3,22 +3,25 @@
 Public Class ActivityFinishedState
     Inherits ActivityState
 
-    Private ReadOnly _employee As IEmployee
-
     'Not from other state.
     Public Sub New(activity As IActivity, employee As IEmployee)
         Me.Activity = activity
-        _employee = employee
+        CurrentEmployee = employee
     End Sub
 
     'From other state.
     Public Sub New(state As ActivityState)
         Activity = state.Activity
-        _employee = state.GetEmployee()
+        CurrentEmployee = state.GetEmployee()
     End Sub
 
     ''' <inheritdoc/>
     Public Overrides Function ActivityStateEnum() As ActivityStateEnum
         Return ActiviteitenOpvolging.ActivityStateEnum.Finished
     End Function
+
+    ''' <inheritdoc/>
+    Public Overrides Function GetEmployee() As IEmployee
+        Return CurrentEmployee
+    End Function
 End Class
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/IEmployee.vb
===================================================================
diff -u -r1730 -r1735
--- ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/IEmployee.vb	(.../IEmployee.vb)	(revision 1730)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/IEmployee.vb	(.../IEmployee.vb)	(revision 1735)
@@ -7,6 +7,12 @@
 
     Property CurrentActivity As IActivity
 
+    ''' <summary>
+    ''' If an employee gets selected, it receives a number.
+    ''' </summary>
+    ''' <returns></returns>
+    Property Number As Integer
+
     Function Equals(obj As Object) As Boolean
     Function ToString() As String
 End Interface
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityState.vb
===================================================================
diff -u -r1729 -r1735
--- ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityState.vb	(.../ActivityState.vb)	(revision 1729)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityState.vb	(.../ActivityState.vb)	(revision 1735)
@@ -3,6 +3,17 @@
 
     Public Activity As IActivity
 
+    Dim _employee As IEmployee
+    Protected Property CurrentEmployee As IEmployee
+        Set(value As IEmployee)
+            _employee = value
+            _employee.CurrentActivity = Activity
+        End Set
+        Get
+            Return _employee
+        End Get
+    End Property
+
     ''' <summary>
     ''' The <see cref="ActivityStateEnum"/> for the current state.
     ''' </summary>
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/Employee.vb
===================================================================
diff -u -r1730 -r1735
--- ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/Employee.vb	(.../Employee.vb)	(revision 1730)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/Employee.vb	(.../Employee.vb)	(revision 1735)
@@ -9,6 +9,9 @@
     Public Property Initials As String Implements IEmployee.Initials
     Public Property CurrentActivity As IActivity Implements IEmployee.CurrentActivity
 
+    ''' <inheritdoc/>
+    Public Property Number As Integer = -1 Implements IEmployee.Number
+
     Public Overrides Function Equals(obj As Object) As Boolean Implements IEmployee.Equals
         If Not TypeOf obj Is IEmployee Then
             'Not the right type.
@@ -20,7 +23,7 @@
         Return employee.Initials.Equals(Initials, StringComparison.CurrentCultureIgnoreCase)
     End Function
 
-    Public overrides Function ToString() As String Implements IEmployee.ToString
+    Public Overrides Function ToString() As String Implements IEmployee.ToString
         Return $"Employee: {FirstName} {LastName} ({Initials})"
     End Function
 End Class