Color image transform coding methods and apparatus which take advantage of redundant information which is normally present in the luminance and chrominance components of a color image are described. The transform coding method of the present invention, can normally provide increased compression and/or better image quality at a given coding data rate than conventional JPEG or JPEG 2000 coding which does not use the transform of the present invention as part of the color component coding process. These benefits are normally achieved without generating more coefficients than would be generated in the case of more conventional coding such as JPEG or JPEG 2000 coding. In fact, the transform of the present invention can be applied to increase the coding efficiency of coding systems which perform spatial transforms and modeling and entropy coding operations of the type normally used in JPEG and/or JPEG 2000 coding systems.