What is "full blood chocolates"? They can still be chocolate even if they are carriers for other colors, in which case there is a chance that they will produce some non-chocolate offspring. It's the same with lavenders, there is usually some chance of producing visibly black chicks from lavender parents. That's usually disclosed by the breeder before purchase. When buying, you should specify what you intend to use the chickens for, because not all varieties breed true. Some won't produce the same results if you breed them to each other, but most people don't breed them, or have mixed flocks, so it doesn't matter.