It has nothing to do with dominant/co-dominant, it's about heterozygous and homozygous. Two animals that are heterozygous for two separate genes will produce 25% each of normal, het for gene A, het for gene B, and het for both A & B.
Dominant, co-dominant, and recessive speak to the nature of the gene itself, and only deals with the way the gene expresses itself in each combination.
Dominant - Both heterozygous and homozygous look the same -- neither appear "normal".
Co-Dominant - The heterozygous and homozygous versions look different from each-other -- neither appear "normal".
Recessive - Only the homozygous version appears different -- heterozygous animals look "normal".
Thanks a lot for the explanation ctrlfreq.. that helps alot . i wasnt thinking of it as heterozygous and homozygous and i was totally confused