In Shorthorn cattle, coat color is controlled by a single gene that can exist as a red allele (R) or white allele (r). The heterozygotes (Rr) have a color called roan that looks less red than the RR homozygotes. However, when examined carefully, the roan phenotype in cattle is actually due to a mixture of completely red hairs and completely white hairs. Should this be called incomplete dominance, codominance, or something else? Explain your reasoning.