Green Bar Matrix =ReportItems!Color.Value Ignored

I followed the instructions and the textbox named Color did indeed display alternate colors on the odd rows.
However, when I tried to propogate the color to the whole row using the expression =ReportItems!color.Value for the value of the backgroundcolor property, it was ignored.

So I tried some custom code:
Public Function GetColor()
Dim retValue as String
retValue = Me.ReportItems!Color.Value
return retValue
End Function

The syntax parser didn't like ReportItems either.
I first tried it without the Me object and I got a message about requiring an object so I tried Me.

Has anyone got another idea?

Thanks,
IanO