ok, i have managed to work out the answer i think here is me vba code

Sub No_Fill_backgroundColour()
With Application
.ScreenUpdating = False
End With
Dim rng As Range, cell As Range

Set rng = Range("B4:B" & Cells(65536, "B").End(xlUp).Row)

For Each cell In rng
If (cell.Offset(0, -1).Value <> "") Then
cell.Interior.ColorIndex = xlNone
End If
Next cell

With Application
.ScreenUpdating = True
End With
End Sub