And not so much for website design, but for interior design, painting or faux finish there is an AWESOME piece of software called CBN Selector
http://www.cbnsystem.com/software/selector_features.asp. You can load an image (e.g., a picture of the living room), frame out different things in the image (the couch, the walls, the floor, the fireplace, etc.), then try on different colors and styles. Now I am sure many pieces of software do this but the thing with this is that
- you have so much precision control on the color
- you can use color chips from all major paints (ben moore, behr, valspar)
- you can then show complementary colors for accent work
Now, I am likely not the best person to plug this software.....my partner is a muralist and decorative paint designer and found this a short while ago and RAVES about it. He constantly is talking about how much this software helps him to his job. So if there are any interior or exterior designers or painters out there, give it a test drive and post your feedback & findings here.
I have no affiliation with the software or company.