Most pigments are pre-mixed, therefore they have 2-3 colours already mixed. Mixing too many pigments can result in creating a “muddy” colour, which is dull and much closer to a grey. You can mix your pigments, but we recommend no more than 2 colours.
Tina Davies pigments are pre-modified; she has created 7 light-to-dark shades and recommends to darken colours by using a drop of either bold brown or ebony. These colours are ultra-concentrated enabling you to place the target colour directly on top of an old pigment that has faded and left an undesired undertone.