Dim CellVal as Integer
For i As Integer = 0 To DGVAlle.Rows.Count - 1
    CellVal = CInt(DGVAlle.Rows(i).Cells(RS).Value)
    Select Case CellVal
        Case 1 : DGVAlle.Rows(i).DefaultCellStyle.BackColor = Color.Blue
        Case 2 : DGVAlle.Rows(i).DefaultCellStyle.BackColor = Color.Red
        Case 3 : DGVAlle.Rows(i).DefaultCellStyle.BackColor = Color.Green
    End Select
Next