Depends. Cheap gel colors (Wilton) don't dissolve all the way into IMBC or SMBC. Well, some of the colors do (yellows, oranges, reds and greens) and some not so much (blues, purples browns and blacks). Higher quality gel pastes are better but not perfect. And, if your IMBC or SMBC has an acid in it (cream of tartar) you wont get "true" blues or purples from gel paste. Purple is a real bee-atch.

Powder colors are ok, but again, sometimes they don't dissolve all the way.

Liquid colors for chocolate (oil based) produce the most consistent results, but they aren't available in the same range of colors as paste and powder.

I wouldn't use generic liquid food color (water based) as it is next to impossible to mix the water into a fat based buttercream, and you have to use wayyyyyyyy to much to get vibrant colors.

It's best to have them all on hand, and experiment... lol

(I know how that sounds...)