I've said it before and I'll say it again. Just because a recessive trait can have "markers" doesn't make it codominant. A "marker" is not the same thing as a visual phenotype. Albino is only albino if it has BOTH copies of the recessive trait.
Piebald is only Piebald when it has BOTH copies of said recessive trait. These affects or "markers" can be caused by pleiotropy or even epistasis as well by many other reasons.
Albinos, piebalds, clowns, etc. all produce a recessive phenotype that is only visible in the homozygous genotype.