You start off defining a subroutine (Sub) and end up closing a function. This alone will not work.

You appear to be expecting to loop through a range of cells, but there is no code to do this.

Following your logic, is something like this what you were trying to achieve?

Sub changeBackColor()
Dim x As Long

For x = 0 To 55
If x = 10 Then
Sheets(“Sheet1″).Range(“A1″).Offset(x, 0).Interior.ColorIndex = 3
Else
Sheets(“Sheet1″).Range(“A1″).Offset(x, 0).Interior.ColorIndex = 11
End If
Next x
End Sub

Sub ColorRef()
Dim x As Integer

For x = 1 To 56

If x 10 Then
CurrentCell.Interior.ColorIndex = 3
Else
CurrentCell.Interior.ColorIndex = 11
End If
End Function