From what I understand first you need to find the dominant colors in the images and store them inside a database. There's a script called color thief that does that beautifully. But chances are all the colors will be different! The color search form can't display all of them. Google search only allows you to pick from 12 colors. If you pick red it will show images that have all shades of red, not just the one you picked
How does color search engine work?
search;search engine;color