We do not use synthetic dyes or micas, which is common in organic artisan soap. The reason is that we want to explore and learn to master a relatively unexplored area of natural colors in soap making. Many synthetic substances also give rise to emissions of heavy metals or are carcinogenic.
The biggest challenge with natural colors is to make them survive the saponification process and then also last over time. They rarely produce exactly the same results time after time due to nature's natural conditions. The colors in the soaps also change over time in step with the saponification and during the storage period. Most naturally colored soaps are best stored in the dark to retain their color as long as possible.
The plant colors I use right now come from indigo (blue and green), alkanna (grey purple), annatto (yellow) and horsetail (red). The black shades come from activated carbon. I get white by using a light soap recipe and adding salts.
Clays also give beautiful color to the soaps and I use kaolin clay which is white, illite which gives yellow, pink and red shades and montmorillonite which gives green shades.