Colourants can be classified as either organic or inorganic and can be added as is or dispersed in castor oil.
Organic colours in the past were derived from coal sources. Currently however they are mostly synthetic. Some are soluble in water, soluble in oil or insoluble in water/oil (Lakes)
Inorganic colours (pigments) consist of insoluble metallic compounds from natural sources. They do not have health risk associated with them and they are insoluble. They can be classed into iron oxides, zinc oxides, titanium oxides, carbon blacks, chromium oxide greens and ultramarines.
Mica’s have many different colours and particle sizes. Mica’s smaller than 20micron give a satin like appearance and Mica’s with a particle size larger than 150micron give a sparkle appearance.