Nature.
I discovered this back in 2007 playing around with images I'd taken out my kitchen window ~ http://www.flickr.com/photos/bootload/sets/72157603995704881... I also keep a hand colour set on flickr for reference ~ http://www.flickr.com/photos/bootload/sets/72157600195794663...
Back in 2007: "If I ever need to do things like come up with ideas observation of nature and complex systems such as the web is always a good place to start. Here I'm looking at colour & colour schemes. Never would have thought of this combo and ratios" ~ http://www.flickr.com/photos/bootload/541666109/
http://books.google.com/books?id=mG-VRWgfpuYC
http://en.wikipedia.org/wiki/Wassily_Kandinsky#Concerning_th...
Kandinsky's book is interesting even if what he is saying is mostly metaphorical. However, some of his observations were spot on as that of describing the case of the German patient with color synesthesia. http://en.wikipedia.org/wiki/Grapheme-color_synesthesia
Fascinating topic!
I've written an article about my take on color psychology in web pages:
http://experimentgarden.blogspot.com/2009/06/psychology-of-c...
I would recommend that you hire a designer, or make friends with some designers who can help you with this.
I makes adjustments over time, the more I look at something while I work on it.
Often I poke around with assorted tools to see what pops up.
This carries through in my designs-
So usually start with a color and may see a site with a scheme and alter it or use one of the color scheme choosers in google
I also use the previously mentioned colourlovers and colorschemedesigner.
As you see the color schemes are only there to accentuate the brand. Do customers buy teslas in order to be green or because their a luxury sports car? Their color scheme is chosen on the basis of their brand and who their customers are.