The backcolor of a command button is set according to the Windows color set selected by the user and cannot be directly changed through VFP AFIK.

There are several solutions to this issue:
1. Change the the Windows color set - not very friendly.
2. Place an image on the button that includes the required text on your preferred color background - close but not perfect.
3. Create your own command buton classes. If you do this you can have flashing buttons, latchable buttons etc.

Hope this helps

(Incidentally I asked Mike Stewart if more features such as this would be available in VFP 7 - but the answer was No. It would be nice to have it in VFP8)