Well, I mean, mitosis is mitosis. You will get an even divide of 50% of the chromosomes from one parent, and 50% from another and form a new individual. But, that doesn't mean that you get an even half of the traits. So here we go back to Mendelian genetics - if you mix a tall plant with a short plant, you're not going to get 100% medium-height plants. Or a red flower with a white flower will not give you 100% pink flowers.
Like with us, my mom is blonde and my father has black hair - I came out with blonde hair and my sister got brown hair. Or you see those families where all the children look A LOT like mom, or they all look a lot like dad, or they look like more or less a good mix of both. In a clutch the same would happen, between one factor and another, you can get clutches that show varying percentages of traits from their parents. Some look like dad, some look like mom, some look like both, and some look like neither.
So to echo what Reptoman said, you have to have lines with very similar traits to increase your chances of the same genes making it to the surface, as it were. For example, my male is a cross but his father is a very blue Faly, and he is a very blue chameleon. When I picked out his girlfriend, I looked for a bloodline with a lot of blue as well. So her father is a pure Nosy be and her brothers look almost like pure Nosy be's as well with a lot of blue. So I have a certain level of certainly that their offspring, even though they're crosses and have more at play, will show a large percentage of blue.