I have used the following in the OnPrint event in the Detail section of numerous reports. You can easily fiddle with the numbers to get your prefered colours. Colours in this example are very pale because I don't want to use excess ink or toner when I print the reports but they are sufficient to make readability better. H'mmm, I'm not sure about the "Light Grey" number but give it a go, you can't get into much trouble.
If Detail.BackColor = 16777215 Then
Detail.BackColor = 14811135
'14811135 = Light yellow. 15263976=Light Grey
Else
Detail.BackColor = 16777215
End If
End Sub