I want to buy a 2lb tub of satin ice gum paste to have on hand and was wondering if to color it i would need to buy fondant to combine with it, or is it possible to just use gel?
You can just use gel colors. If you need bright colors though, it will get massively sticky from all the coloring I usually mix gumpaste with at least a little fondant to make it more workable. That has no effect on the coloring, though.
I used americolor to color my Satin Ice gumpaste direct without adding any fondant to it. Worked just fine.