Dithering

[Mark Overmars]

If I use double buffered drawing on a Personal Iris I have only 12 bitplanes.
Now the machine start using dithering when working in RGB mode. My first
question is:

 - Can you switch off dithering?

If not my second question is:

 - How should I choose my color such that there is no dithering?

I thought this where multiples of 16 but that does not seem to be correct (or
is it)?

Mark Overmars