Thanks for the tip about the colored wax chips, and I'm glad that the crayon doesn't cause any fouling issues.
However the same outfit also sells liquid soap dye that could be used like the colored wax chips. The color selection is limited but the soap dye is also described as being very concentrated.
Your lube came out to be very colorful though, and the crayons seem to work great. I just wasn't so sure about the composition of the crayon wax and its interaction with black powder. Some crayons might be different than others.
Product ID: SC5040
Liquid Soap Color
Each bottle of these highly concentrated soap colors are formulated for you to use in coloring your soap products. Each 1oz bottle will dye between 5 - 10 pounds of soap, depending on how intense you want the color. Soap Color: