I present a model which describes the effects of bandwidth and peak replay wavelength shifts on the image color of color display holograms. The model applies to white light reflection holograms recorded with three component colors, but is also applicable to other types of color holography such as pseudocolor techniques. A computer program is used to transcribe the predicted spectral power distribution of the color hologram into coordinates plotted on a standard chromaticity diagram. The increase in bandwidth between recording in laser illumination and replay under white light causes a proportional shift of the replay color towards white, and is thus one of the causes of desaturation found experimentally in color holograms. The model is used to show the shifting of the image color when the peak replay wavelengths of the component holograms are changed as a result of shrinkage or swelling of the recording medium; this can have devastating effects on the image color reproduction, especially when the peak of the red or blue components moves to a longer wavelength.