There is a product called Deep that allows you to search by color pallette.
Deep calculates the range of colors used in each of your images by analyzing the pixels and calculating the most popular colors. This is what makes the palettes in Deep powerful, you can find images that have similar colors, which is great when you are looking for the perfect picture to go on your web site. In fact, just drag any image on to Deep and it will find and rank all the images on your computer that are similar.
There is even a YouTube video demoing its usage so you can get an idea of how it works prior to downloading, installing, and purchasing.