What an interesting question! I may be "colored" myself by Colin Firth's Darcy in my favorite version (BBC) of Austen's novel, but here is what I think.

His feelings would be painted a bluish-grey. Darcy is part of the elite class, and blue is the traditional color of royalty. But a subdued nature would infuse the blue, making it grey. Darcy's feelings, until the very end, are pervaded by sadness and longing and unfulfillment.

His manners I would say are golden, but a fiery gold, not a muted color. He can certainly get his ire up, but he demonstrates ultimate good manners in his handling of the disastrous Lydia situation.

His pride is a royal purple, like the color of veins beneath his alabaster skin. His pride fuels him, sometimes to his benefit, sometimes to his detriment.

So, here's my vision of Darcy in his finest suit: Blue-grey, crisp white shirt, gold watch and links, purple ascot. How's that for a picture? :)