In the diverse world of Natural Dyes, there are a number of biomolecules that create color. Tannins are a large group of astringent, polyphenolic biomolecules that abound in the plant kingdom and they are used for their own colors as well as act in symphony with other biomolecules & metals of salts (iron, for example) to make a wide range of natural dye colors. Here are examples of 3 major classes of tannins: the "clear", "yellow" & "red" tannins.
On the left is a Clear Tannin, upper right a Yellow Tannin & lower right a Red Tannin, each is shown with & without iron (a metal salt).
Curious to learn more? Join my Become a Home Natural Dyer Workshop, which starts in just a few days, April 22nd, Earth Day! A 4-week online workshop with video & live zoom demos, lots of support materials & Q&A time.