...but this is a topic I actually know something about!

You may be surprised to know how difficult it is to get any real color from natural sources in New England. You can try sumac berries, dandelion roots, beets, the bark of a crab apple tree, Rosehips, chokecherries, dried hibiscus flowers (red or dark pink), or wild ripe blackberries -- if you can stand the thorns! I've tried the sumac berries and the blackberries with little luck. Dried hibiscus gave me a light reddish-pink, but it was not very washfast.

The best blue I've ever gotten was from red cabbage, which is at least very easy to grow or buy, but it was a light blue and not especially washfast. You can get nice yellow/orange colors from onion skins, goldenrod, and jewelweed. There are also a lot of wildflowers/weeds that supposedly give good color... And I almost forgot Coreopsis Gigantica - which will give a spectacular and near permanent orange color if you do it all just right, which is entirely more trouble than almost anybody would want to go through...

Natural dyes are not only more complicated and "fussy" to work with than chemical dyes, but they're surprisingly more toxic. Go figure.