Changing command button colors using variables

Hi

I have been trying to use VBA to change the color of a set of command buttons using variables rather than individually in code. Individually no problem using

ActiveSheet.CB1.BackColor = RGB(x, y, z)

where CB1 is the button.

I can change the color of Excel shapes with variables using the following syntax

ActiveSheet.Shapes("Shape" & a).Fill.ForeColor.RGB = RGB(x, y, z)

however changing command buttons using this syntax does not work, surprisingly it does not give an error but does not change anything either.

Using variants of both code segments I have tried as many as I can find and so far have been unable to achieve the color change.

If anyone has any pointers they can give me it would be much appreciated.

Many thanks

Jeff