Do you mean a form with contols on it, and you want to change the colour of everything? Or just a blank form, or what?
For a blank form, just do two nested For loops. One to count across the form, one down. At the intersection, use <formname>.Pset to set the colour.
That's the slow version. Setting the BackColor property would have much the same effect, only faster.
Try playing around with this stuff - don't just sit there waiting for an example, it's more fun to work it out for yourself.