An excerpt of an excerpt:

Because of the high cost of commercial dyestuffs, and because many rural early Americans did not have immediate access to trading centers, some settlers planted the seeds of familiar dyestuffs in their gardens to ensure the availability of coloring materials. Woad (Isatis tinctoria) for blue was a popular garden dye plant, although it exhausted the soil and thereby necessitated the constant opening of new tracts of land (Stearns 1964).

European settlers also experimented with the unfamiliar native plants that they discovered within their new environment. They encountered local species related to their European dye plants, such as a North American sumac (Rhus species) similar to the "diar's shumach" of England. They also encountered completely new dye sources. While some individuals shared the results of these discoveries with neighbors, others did not. Reportedly, one colonial housewife in New England formulated a process for obtaining a rare pink color but refused to divulge the source of this dye and took the secret to her grave. That particular hue became known as Wyndym pink, named after the town in which she lived (Harbeson 1938).

European settlers also learned about American dye plants from resident Native Americans, who produced red from bloodroot (Sanguinaria canadensis), green from algae, and yellow from lichens. The poisonous fruit of pokeweed (Phytolacca americana), an indigenous North American herb, was favored by Native Americans as a colorant for baskets (Weigle 1974). The American colonists observed, however, that many of the hues produced by Native Americans quickly faded, suggesting that mordants may not have been used.
The book Dyes from American Native Plants looks to be a good source, though I'm still interested if anyone here has any practical knowledge/regional specificity.