TinEye is a search engine of identical images on the web. But it also has two other tools from his experimental laboratory: Multicolr Search Lab and Color Extraction.
So like Flickr options, but with a friendly and preconfigured interface (select only Creative Commons licensed images), Multicolr Search Lab finds images on Flickr that correspond to different colors (one to five) you have selected beforehand.
To choose a hexadecimal color, select a color and click it to display the settings and specify the hexadecimal number.
You can also enter keywords to narrow down your search.
TinEye also offers color extraction tool that retrieves different colors composing an image.