The "classic" couplers are colourless.
By giving the coupler a hue of the same kind as unwanted hue is built up parallel to the formation of the image-foming dye, you gain a equal stain instead of an image depending one. The former can easily be filtered out.
This automated masking is employed in systems that need copying as in negative-to-paper.
This all is done because the image-forming dyes are not optimal, and the unwanted effect is enhanced during copying on similar material.
This automated masking is one major invention in colour photography.
Though, as hinted at there are materials that by choice do not employ such masking but to an extend cope otherwise.