The term co-dominant is used incorrectly by reptile enthusiasts. The proper term is “incomplete dominant”
However, the common usage in the reptile industry is:
The genetic pattern of co-dominant genes is essentially the same as the genetic pattern of the simple recessive genes, except, that heterozygous “het” animals are visibly different than normal animals. These visible “hets” can be bred together to produce a mutation, called a “Super”. The Super, is also the dominant form of a co-dominant gene.
“Het” animals are just non-visual co-dominants. However we are learning at all times. Many times these “non-visual” hets have just very subtle changes, that are hard to see. This is where “markers” come in. Many say they can usually tell a Het Albino or Het Pied by its markers. This would actually make them co-dominant instead of recessive, but just VERY subtle.