Changing range in VBA to lastrow

So i have this VBA code

Option Explicit

Sub ValuesByColors()

Const Blk = 0
Const DkGray = 65535
Const LtGray = 12632256
Const OW = 16777215
Dim r As Range

Application.ScreenUpdating = False


For Each r In Range("A1:Q11").Cells
    Select Case r.Interior.Color
       Case Is = Blk
            r.Value = 0
       
       Case Is = DkGray
            r.Value = 3
       
       Case Is = LtGray
            r.Value = 10
                 
        Case Is = OW
            r.Value = 21
    End Select
Next r

Application.ScreenUpdating = True


End Sub

but i want the range of which
"For Each r In Range("A1:Q11").Cells"
to change to last row but the following does not work

Option Explicit

Sub ValuesByColors()

Dim lastrow As Long
 lastrow = Range("A" & Rows.Count).End(xlUp).Row

Const Blk = 0
Const DkGray = 65535
Const LtGray = 12632256
Const OW = 16777215
Dim r As Range

Application.ScreenUpdating = False


For Each r In Range("D1").AutoFill Destination:=Range("D1:S" & lastrow)
    Select Case r.Interior.Color
       Case Is = Blk
            r.Value = 0
       
       Case Is = DkGray
            r.Value = 3
       
       Case Is = LtGray
            r.Value = 10
                 
        Case Is = OW
            r.Value = 21
    End Select
Next r

Application.ScreenUpdating = True


End Sub