I make a body butter that has shown to be really good from a therapeutic standpoint so I try to keep it as "natural" as possible. Any good suggestions for colorants that are reasonably natural? I've thought about just using food coloring.
Wilton cake coloring gel might work. It works in bath bombs and bath salts. Just make sure not to use to much at a time. Colored skin-safe clays might work too.
If your recipe is anhydrous (no water), then food coloring might not work as well as you'd like. I'd look at cosmetic clays like lsg suggested. Or do oil infusions of spices -- annatto seed infused in oil is yellow for example.