Which Plant Gives Which Colour

A chart matching source species to colour, lightfastness and historical use, from Lascaux to 1869.

Ochre, an iron-oxide earth pigment, is among the oldest art materials; the cave paintings of Lascaux in France, about 17,000 years old, use ochre reds and yellows. As a mineral it does not fade the way organic dyes do, which is why those reds and yellows survive in the rock.

Indigo is a blue dye extracted from plants such as Indigofera tinctoria. The dye molecule is reduced to soluble 'white indigo' in a vat before cloth is dipped and oxidized blue in air — the blue only appears when the reduced form meets oxygen.

Madder root, Rubia tinctorum, gives reds through the compound alizarin; it was the main red dye of Europe until synthetic alizarin arrived in 1869. That date marks the end of madder's dominance, though the root is still used.

Walnut ink is made by simmering the green husks of walnuts, Juglans regia, and straining the brown liquid. The colour is a warm brown and its strength depends on how long the liquid is reduced after straining.

Lightfastness separates plant colours: indigo and madder last well, while many berry and flower dyes fade within years in daylight. If a colour must survive, choose one of the two proven dyes or an earth pigment.

Lake pigments are made by fixing a dye onto an inert base such as alum, turning a soluble plant dye into a usable paint pigment. The lightfastness of the result is the lightfastness of the parent dye — fixing it onto alum does not make a weak colour stronger in light.

• Ochre — iron-oxide earth — reds and yellows — mineral, stable
• Indigo — Indigofera tinctoria — blue — holds well
• Madder — Rubia tinctorum — red via alizarin — holds well until 1869 synthetic replacement
• Walnut — Juglans regia husks — brown — ink, batch-dependent
• Berry and flower dyes — various — many hues — fade within years in daylight

Further reading

• Making Walnut Ink
• Binders: Gum Arabic and Egg