Pigment colours are usually not suitable for water-soluble products such as liquid and solid soaps, as the pigments sink to the bottom.
They can also discolour your bath and sink. Titanium Oxide, however, works well for colouring Solid Glycerine Soap white, without discolouring sinks or baths.
These Normal Pigment Colours can easily keep without fading for 7 years in an airtight container; just don’t store them in direct sunlight.
They’re best stored in a dry and dark place.