1. A computer-program product, tangibly stored on machine-readable medium, the product comprising instructions to cause a computer to: retrieve images from an image data store; generate a global color table for the image data store; for each of a plurality of original images in the image data store, estimate an estimated number of distinct colors in an original image, use the estimated number to determine a number N of colors to use to represent the original image as a quantized image, map each of the quantized image colors to a resultant color in the global color table, and generate a color feature vector of color descriptors to represent the image; receive a query comprising a query image; use the query image to create a query color feature vector of one or more descriptors, each descriptor comprising a color index that references a location of a color in the global color table; and compare the query color feature vector to the color feature vectors of the plurality of images to identify images among the plurality of images that satisfy the query.