jhall

I think you had your explanation of incomplete and codom right the first time.

I can't speak for ball genetics, but can give you examples of human genetics.
Codom traits are traits where two dominant alleles are expressed together. A very good example of this is the ABO blood group. Blood types are controlled by 3 alleles, A, B. and i (being recessive to both A and B creating type O blood when the gene is ii). A person who has both A and B alleles will have type AB blood as both alleles are expressed TOGETHER.

Much like roan cattle, the two colors of hair are both expressed, not blended.

Incomplete dominant traits are traits where you have two dominant alleles at a loci but they are expressed in a blended form in the phenotype (this is sometimes also reffered to as intermediate expression). One example in humans is hair type. Hair is controlled by two alleles one for straight hair and one for curly. Someone who has straight hair is homozygous for straight (2 of the same allele). Someone who has curly hair is homozygous for curly. Now if someone has one straight allele and one curly (being heterozygous), it would present in the phenotype as wavy hair, with neither allele being completely dominant over the other, it would show as a blending of the two.

Another example of this is some flower colors (ie. carnations). If a carnation had one red allele and one white allele it would show as a pink carnation.