I found that if you set the Style of the "Combo Box" to "4-Colors" it will allow you to pick a color from the standard autocad pallet. I would like to ask the user for an RGB (Red Green Blue) value and only an RGB, no other pallett or color code would be allowed. Only RGB, is this doable?
I don't think there is any way to prevent someone from choosing a standard color from the true-color selection dialog, but maybe it would be enough to just convert the selected standard color into the equivalent RGB color after it is selected.