Cosmetic colour is regulated: only colorants on the permitted lists may be used, and some only in certain product types.
Permitted colorants
In the EU, Annex IV of the Cosmetics Regulation lists permitted colorants by Colour Index number, with conditions such as "not in products applied near the eyes" or "rinse-off only". In the USA, FDA rules distinguish certified colours (batch-certified, such as FD&C dyes) from colours exempt from certification (such as iron oxides and ultramarines). India's cosmetics rules refer to BIS standards for permitted colours.
Why dispersions
Dry cosmetic pigments are dusty, hard to disperse and can speck. Pre-dispersed colour in a cosmetic carrier such as glycerine or a cosmetic ester mixes in quickly and gives reproducible shades.
Soap-specific points
- Toilet soap is alkaline: choose colours stable at high pH
- Some dyes migrate or fade in bars; pigments are more stable
- Fragrance can shift colour; test with the final perfume
