Well basicly you take a dino that you want to breed, for example rex. Than you need hp, a bit of stam, and melee dmg. You take the best rexes you can find in hp amd melee and keep them unleveld. Sooner or later you will get a mutation, (Colors isnt always visible since they sometes mutate on unused regions in that species) once you get a mutation you have to find out what the mutation is (this is why you want to keep breeders unleveld and unimprinted) on rexes you only keep the HP, Stam, weight and md mutation (thats what i do) if not kill and try again. Eventualy you will get a baby with a good mutation, from than on you new generation starts, use that mutated baby in your breeding to get more and more mutations. And basicly you keep on repeating it until you have the stats you want.
hope this helps you out! If not let me know and il get in touch :D