1. A computer-implemented method, comprising: under the control of one or more computer systems configured with executable instructions, defining a number of color families, each color family including a plurality of color values; determining a color value of the plurality of color values for representative colors associated with pixels of an image, the color value comprising a first color within a threshold distance of a second color that corresponds to the representative colors; assigning the representative colors to one or more color families of the number of color families, wherein the assigning is based at least in part on the threshold distance; and combining histograms of the representative colors and the one or more color families to provide a descriptor of color variation for the image, wherein the descriptor is at least a basis for digital searching of the image.