I've been reading Nan Shepherd's The Living Mountain and have been struck by passages describing colours. Here are three:
When [Cairngorm water] has any colour at all...it is a green like the green of winter skies, but lucent, clear like aquamarines, without the vivid brilliance of glacier water. Sometimes the Quoich waterfalls have violet playing through the green, and the pouring water spouts and bubbles in a violet froth. The pools beneath the waterfalls are clear and deep. I have played myself often by pitching into them the tiniest white stones I can find, and watching the appreciable time they take to sway downwards to the bottom.An ordinary human can perceive a million different colours. English has, perhaps, a few thousand of words to distinguish them, and in most normal speech we use far fewer. Deploying a relatively limited vocabulary, Shepherd nevertheless achieves -- with the cooperation of the readers powers of memory and imagination -- subtlety, depth and surprise both with regard to colours of the mountain and the other things she is also writing about when she writes about colour.
Some of the lochs are green. Four of them bear this quality in their names - Loch an Uaine. [The lowest of them, Ryvoan Loch] has a lovely frieze of pine trees, an eagle's eyrie in one of them, and ancient fallen trunks visible at the bottom through clear water. The greenness of the water varies according to the light, now aquamarine, now verdigris, but it is always a pure green, metallic rather than vegetable.
Once the snow has fallen, and the gullies are choked and ice is in the burns, green is the most characteristic colour in sky and water. Burns and rivers alike have a green glint when seen between snow banks, and the smoke from a woodman's fire looks greenish against the snow. The shadows on snow are of course blue, but where snow is blow into ripples, the shadowed undercut portion can look quite green.A snowy sky is often pure green, not only at sunrise or sunset but all day, and a snow green sky looks greener in reflection, either in water or from windows, than it seems in reality. Against such a sky, a snow covered hill may look purplish, as though washed in blaeberry. On the other hand, before a fresh snowfall, whole lengths of snowy hill may appear golden green. One small hill stands out from this greenness: it is veiled by a wide-spaced fringe of fir trees and behind them the whole snowy surface of the hill is burning with vivid electric blue.
The air is part of the mountain, which does not come to an end with its rock and its soil, It has its own air; and it is to the quality of its air that is due the endless diversity of colourings. Brown for the most part in themselves, as soon as we see them clothed in air the hills become blue. Every shade of blue, from opalescent milky-white to indigo, is there. Then the gullies are violet. Gentian and delphinium hues, with fire in them, lurk in the folds.