It's kinda funny how many people sound like they know exactly what they're talking about and yet they don't. And I don't mean that to sound condescending, but if you don't know, maybe say you're not sure instead of sounding like an expert. Some of the feedback is correct (HCG, Cardinal, Gonewest)... Some of the other posts contain some statements that are correct, but the post may not be completely accurate. Some of the statements that have been made are just wrong.
Basic color genes are black (dominant), red (recessive), and white, which is what you find in white or roan Shorthorns...not Charolais. A white Shorthorn is white; roan coloring is an example of shared dominance...neither gene is completely dominant, and so both are expressed...some white hairs and some black or red hairs. The dilution gene that Charolais are known for is a color modifier, not a color. Charolais are not genetically "white" but homozygous for the dilution gene which is dominant over non dilution. When you cross a Charolais with an Angus, you get smoke because black is dominant over red (which Charolais have) and dilution is dominant over non diluter. A smoky colored animal, regardless of breed make up, has at least one gene for black and carries a dilution gene, diluting black color to gray. That animal may be either heterozygous or homozygous for the black gene and still be gray, meaning it may or may not have a red gene. If it has one red or yellow parent, you know it is heterozygous black (one red gene) because red is recessive. Since there's no distinguishing line that separates red or "orange" cattle like the line between black and gray, you can't necessarily look at a red animal and know whether or not it carries a diluter gene. If a red animal has two black parents or two non diluted parents, it's non diluted. There are plenty of non diluted "orange" cattle that have two black parents. In general, though, if you're not sure, typically the lighter the shade, the more probable the chance that a red animal does carry a dilution gene, especially when you get into a color you would consider "yellow" and not red. If this is confusing, think about the variance in shades of red in the Hereford population which does NOT have a dilution gene.
To answer your original question, I think HCG nailed it for you. Wild type color alleles and color patterns are what makes the whole thing fun!
