Create a separator

I want to create a colored line after each execution of this code between each execution or to color the last section.
In the code below, how can you create a colored blank row at the end of the operation?

Sub CopyHighlightedTransactions()
Dim mycell As Range
Dim myrange As Range
Dim lastrow As Long
Set myrange = Worksheets("sheet2").Range("a2:a1000")
myrange.Interior.Pattern = xlnon

Dim mc As Range
Dim my As Range
Set my = Worksheets("sheet4").Range("a2:a1000")
my.Interior.Pattern = xlnon
For Each mc In my
  For i = 1 To 10
    If mc.Value = Application.WorksheetFunction.Large(my, i) Then
      mc.Interior.ColorIndex = 4
      mc.Resize(1, 16).Cut Destination:= _
            Worksheets("sheet5").Range("a1").Offset(Worksheets("sheet5").Rows.Count - 1, 0).End(xlUp).Offset(1, 0)

    End If

  Next
Next mc

Worksheets("sheet5").Columns.AutoFit
End Sub

I want to create a colored line after each execution of this code between each execution or to color the last section.

Please, try the adapted code. It calls markLast which colors in black the interior of the empty row after the last one:

Sub CopyHighlightedTransactions()
 Dim mycell As Range, myrange As Range, lastrow As Long
 Dim ws2 As Worksheet, ws4 As Worksheet, ws5 As Worksheet

 Set ws2 = Worksheets("sheet2")
 Set ws4 = Worksheets("sheet4")
 Set ws5 = Worksheets("sheet5")

 Set myrange = ws2.Range("a2:a1000")
 myrange.Interior.Pattern = xlNone 'supposing that you do not need any pattern...


 Dim mc As Range, my As Range
 Set my = ws4.Range("a2:a1000")
 my.Interior.Pattern = xlNone 

 For Each mc In my
    For i = 1 To 10
        If mc.Value = Application.WorksheetFunction.Large(my, i) Then
          mc.Interior.ColorIndex = 4
          mc.Resize(1, 16).Cut Destination:= _
                ws5.Range("a1").Offset(ws5.rows.count - 1, 0).End(xlUp).Offset(1, 0)
        End If
    Next
 Next mc

 ws5.Columns.AutoFit

 'color the interiror of the empty row after the last one in black:
 markLast ws5
End Sub

Sub markLast(ws As Worksheet)
     With ws.Range("A" & ws.rows.count).End(xlUp).Offset(1)
        .Value = "."
        .EntireRow.Interior.Color = vbBlack
     End With
End Sub

If xlnon is not a custom pattern, it should be xlNone if you need to clear the pattern. To be none... In such a case, please write Option Explicit on top of the module (in the declarations area). It will force you to declare all variables and it will warn you in case of a typo.

And take care of the code indentation. Without it, if the code becomes complex it would be very difficult to understand and debug it.