Reds--madder is reasonably easy to grow and very prolific. Wouldn't have been expensive, as far as I know, and it does a nice rusty red. Greens--many yellow dyes will produce green if dyed in an iron pot, or with iron added. Another way of doing it is to overdye woad with a yellow dye, which may account for the cost, if using indigo, but woad was fairly prevalent in Europe. Other greens that apparently were used in Scotland (according to Wikipedia): privet berries with salt, cow weed, broom, heather, iris leaf (iris blossoms are used to make verdigris, green paint, and from the example I was shown, it dyes cloth just as well).