If it is a commandbutton from the control toolbox named CommandButton1 on Sheet1, then this hex number will change the color of that button to green
Worksheets("Sheet1").CommandButton1.BackColor = &HFF00&
If it is a commandbutton on a userform, with the userform active, simply
CommandButton1.BackColor = &HFF00&
You can see the hex numbers in the Properties window of any command button. Personally I prefer color command using hex rather than color names or color index; you may gravitate more to color names or index, it's a matter of preference.