Highly concentrated D&C grade (drug & cosmetic) dyes are great for melt & pour soaps and lotion/gel bases too. Each dye comes with a dropper top so it's easy to measure the amount of dye (D&C #40).
We used 1 drop per ounce of base for our pictures. Using more will result in a deeper color and using less will give you softer, more pastel shades.
Liquid soap dyes are water soluble therefore should NOT to be used in Cold or Hot Process soaps.