Chocolates are the next-to-rarest color of the four "REAL" colors (there are all sorts of ugly weird ones like Tortie-Point - looks like the cat got left out in the rain). The Seal is dominant, the Blue is a recessive, so a Seal may carry a Blue gene but a Blue will not carry a Seal gene. To complicate matters there is a separate recessive "dilute" factor which will turn a Seal into a Chocolate or a Blue into a Lilac. A Lilac is Blue + dilute (two recessives) and when bred to another Lilac will always give you nothing but Lilacs. Seals may carry both the blue and dilute factors, Blues may carry the dilute factor, and Chocolates may carry the Blue factor since they are a "Seal dilute". (Boy - I bet that doesn't make much sense. Even to me.)
The colors are controlled by heat - the pigment is heat-sensitive and will "burn out". My middle cat for reasons best known to herself likes to sleep with the right side of her face pressed against one of the hot air registers - so she has a little grid pattern in her mask on that side. It looks REALLY weird, but she's happy and she's not shown, so who cares? The big guy sleeps in the bathtub in hot weather, so his sides are VERY dark!
I sort of understand your genetics lesson and hope I won't forget it - no, I'm going to paste it into Notepad and read it a few more times.
Okay, so if I heated up the cat, she might lighten up? Do people who show theirs have techniques, like putting sweaters on them?