To choose and mix colors well you need to understand the properties of the pigments they contain. Each pigment has different characteristics and these influence how it will interact with other pigments. Pigments can be mineral sourced or synthetic. The earliest pigments started life as naturally occuring substances found in the ground, such as umber and sienna. Others were originally derived from natural substances but are now synthetically made. And others have been invented in the lab as the by-product of a chemical reaction! The key things to look at when choosing a color, are pigment type, opacity, lightfastness and strength. Some pigments have a strong tinting strength and will create color mixes that are crisp and bright, while others tend to gray down when mixed. Some pigments will be transparent, others semi-transparent and others completely opaque. Some pigments are stable and can withstand exposure to light without changing. Others will change instantly when exposed to light and this isn't great if you are working on a piece you want to last. Liquitex labeling gives you the pigment codes each color contains, plus details of its opacity and lightfastness.