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Several natural plant dyes were used for the classical colored clothing worn by historical figures. For example, the red coats worn by British soldiers during the American Revolutionary War were colored by a crimson dye from the roots of madder (Rubia tinctorium), a member of the madder or coffee family (Rubiaceae). Madder is a perennial herb with leaves in whorls of 4-5 or more at the nodes. A related and similar-appearing weedy species in California is called bedstraw (Galium aparine), so named because bunches of the plant were used like straw for bedding. The famous gray coats of the Confederate Army in the Civil War were colored with a dye from butternuts (Juglans cinerea) of the walnut family (Juglandaceae). Another natural dye used by ancient Greek and Egyptian women to color their hair reddish-brown was obtained from the leaves of henna (Lawsonia inermis) of the loosestrife family (Lythraceae). Because of its affinity for protein, henna is still used to this day as a hair rinse.

To make some of these natural clothing dyes colorfast (so they wouldn't wash out of the fabric), it was necessary to use various mordants such as mineral salts of tin, aluminum, iron and chromium. In ancient times these mineral mordants came from the metal vessels in which the dyeing was done. In some cases, mordants were added to the dye mixture, including urine and dung. It is a well-known fact that ammonia from urea makes an excellent mordant for certain dyes. Chemically, the mordant helps to bond the dye molecules to the fiber molecules of the fabric. The actual bonding of classical dye molecules with the cellulose polymers of the fiber involves complex hydrophobic interactions and hydrogen bonding. Madder is a particularly good dye because it contains natural mordanting agents. During the Middle Ages, people who made and dyed hats (called hatters) often used heavy metals in their dye baths as mordants. Because they did not wear protective gloves, some hatters absorbed toxic levels of heavy metals causing them to become mentally deranged; hence, the term "mad hatter."

Just as the printing industry was replaced by computers, the dyeing industry was revolutionized by the discovery of synthetic dyes. During the latter half of the 19th century, synthetic dyes were being produced from derivatives of coal tar (from high temperature carbonization of bituminous coal). These dyes (called aniline dyes) produced a wide array of vibrant colors that were much more colorfast than even the best natural dyes. There are, however, many people today who still prefer natural dyes because of health concerns about the safety of synthetic dyes, particularly if they are ingested or come in contact with sensitive areas of the skin.

One of the most interesting natural blue dyes comes from the leaves of a wild mustard called woad (Isatis tinctoria). Woad was introduced into the United States from Europe during colonial times. It is a widespread and colorful, biennial or perennial herb that has become a naturalized weed in some states. In fact, there is some speculation that early German names for woad (weedt, etc.) may have given rise to the modern word "weed." Although true indigo (Indigofera tinctoria), a member of the legume family (Fabaceae), was perhaps a superior blue dye, woad continued to be a popular blue dye in Europe. [Indigo was an extremely important trade item between India and other parts of the world for thousands of years.] Actually the active dye ingredient of woad is the soluble glucoside indican, the same dye found in the unrelated indigo. According to the textbook for this course Plants In Our World by B. B. Simpson and M. C. Ogarzaly (1995), woad was one of the dyes used to make the green outfits worn by Robin Hood's men deep in Sherwood forest. Their clothing was dipped in a blue dye bath of woad, and then in a bath of yellow weld from the leaves of Reseda luteola, a member of the mignonette family (Resedaceae). The mixture of blue and yellow produced the characteristic green color associated with England's legendary bandit who robbed from the rich and gave to the poor. Apparently, the fermented, pulpy masses of woad leaves produced such a foul stench that early woad dyers were prohibited from heavily populated urbanized areas. In fact, Queen Elizabeth I (1533-1603) decreed that no woad processing could take place within five miles of her residence.

Another little-known red dye called alkannin (also spelled alkanet) come from the roots of dyer's bugloss (Alkanna tinctoria). Alkannin is a deep red phenolic dye that is soluble in oils, alcohol and ether but not in water. Several members of the Boraginaceae contain alkannin, including dyer's bugloss (Alkanna tinctoria). It was used to dye textiles, vegetable oils and wine, and is commonly used today as a food coloring. In addition, it reportedly has wound healing and anti-inflammatory properties.

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