These colorants have been tested in cold process soaps and survive the high pH levels of soap. They do not morph and the colors stay true. The oils you use will greatly affect the color results, so if you are using a greenish olive oil, this will change the results.
You can use up to ½ teaspoon for a Kg of soap. Mix 1 teaspoon of colour with 1 tablespoon of 99% isopropyl alcohol or with glycerine before adding it into the soap.