Well, depends on what shade of green etc. you're talking about.  I've seen some brilliant green wools, and there's evidence for green linen and cotton as well.  Here's an excellent article on medieval dyes; the same technology would have been inherited, and improved on, by the 17th and 18th centuries. For more on 18th c. dyes, see this article, and read

Liles, J.N.. The Art and Craft of Natural Dyeing: Traditional Recipes for Modern Use. Knoxville, Tennessee: The University of Tennessee Press, 1990.

I think the reaction against colors stems from a couple of things: a) Hollywood -- which clothes extras and commoners in movies in drab colors so they fade into the background on-screen, and b) the (mistaken) idea that vegetable colors were drab, when in fact you can get vibrant colors from natural dyes, though you might not be able to get neon green or mauve.  You have only to read the runaway ads in the Pennsylvania Gazette to see that ordinary folks wore lots of bright color.  In addition, most dyeing wasn't done at home.  The popular misconception that most of the clothing worn in the colonial period was homespun and hand-dyed is far from true.  You have only to look at the inventories of ships bringing fabric into ports like Philadelphia to realize how much fabric was imported; and ads in the Pennsylvania Gazette (see below) show that even locally produced fabric was frequently professionally dyed -- in a multitude of colors.

A friend of mine sells knitted caps.  The most common documented color of 17th and 18th century knitted caps was red.  However, when she knits red caps, they don't sell, because guys think they can't wear anything but... brown.  Brown caps sell like hotcakes.  Folks, this is NOT RIGHT!  Yeah, brown caps were worn, but when the reenacting community is wearing ONLY brown caps, rather than a nice mixture of red, blue, green, black, and other colors, we're being inaccurate.  So buy some non-brown caps, PLEASE!

Some advertisements from the Pennsylvania Gazette on dyes:

ITEM #19312
March 11, 1756
The Pennsylvania Gazette

NOTICE is hereby given, That JOHN HICKEY continues to carry on the business of dying and linen stamping as usual, in Second street, and purposes to give the publick encouragement by doing any thing that he undertakes, as well as done in Europe, and at as reasonable prices;
<snip>
he takes all manner of stains or spots out of silk of cloth, dyes linen or woollen blue, green, red, yellow, purple, or any other colour; dyes and dresses tammies, camblets, poplins or any such like stuff, in the English manner, dyes leather any sort of cloth colour, and has a glaizing engine for chints or calicoes, scowers and renews the colour of scarlet in a particular manner.
------------------------------------

ITEM #76373
January 6, 1790
The Pennsylvania Gazette

Just imported from England, and to be sold, by WILLIAM CRAIG,
At his store in Second street, opposite the Baptist Meeting,

A NEAT assortment of yard wide and 78 Irish linens, and white and brown
Irish sheetings, white Russia sheetings and white Raven's duck, Irish and
Dutch dowlasses, Scotch shirtings, a linen of a strong fabric, oznabrigs,
cotton stripes, white and brown buckrams, brown silesias, Scotch threads,
from No. 7, to 70, coloured ditto, best Baladine sewing silks, scarf twist,
worsted and hair cord for cloaks, mohair buttons, Dunscomb and metal ditto,
silver plated ditto, worsted bindings, shirt buttons, India bandanoe
handkerchiefs, blue and << red linen>> ditto, scarlet serge bobbins, tapes,
silk Marseilles quilting, Joans spinning, moreens, durants, sattinetts,
double and single worsted damasks, calimancoes, crapes, printed 
cottons and callicoes, muslins, fans, red flannels, white ditto, corduroys, ribbons,
cambricks and long lawns, White Chaple needles, pins, spades and shovels,
frying pans, brass kettles, best F.F. gun-powder, plated bridle bitts,
sadlers webb, stirrups, blue plush, tea spoons, silk velvets, mens and
womens beaver pelt gloves and mitts, short pipes, best bohea tea, red lead,
also good upland and meadow hay in a barn near the city. He would let on low
terms, about 10 acres of meadow ground on Greenwich, to any person that
understands raising hemp.