I was wondering is it possible to just paint the fondant with food coloring or is mixing it in with the fondant the only way?
To paint on fondant either mix your food coloring with vodka, or clear vanilla and paint away. The alchol from the vodka evaporates.
it mays take several days to dry if you paint directly on fondant.
I've been told to use powder colours mixed with vodka rather than gel paste.