Not sure how much room you have, but if you can afford to, I would save all the females born without mutations, and add them to the breeding pool. Then you can breed a whoole bunch each time you are on, and increase your chances of getting a color mutation. Since I am assuming you are starting with high level breeding parents, the offspring should be good too. Then once you get the colors you wanted, you can re-focus on improving the stats is that is your desire. I know, easier said than done.
I currently have around 25 females and 5-6 males used in my breeding pen. All color mutations are saved and moved to another area. All non color mutations starve or are killed.(Then fed to the survivors) I've gotten most of the color mutations I want, except still no Bright Red body, Neon Blue Body, Neon Yellow Spine, or Black body. once i get those, I will replace all the current breeders with all the Color mutated and wait for the rainbow explosion!
last night I got a bright red spine (first time ever getting one of these) a Pink Spine, Sku Blue body, Lime Green belly, and maybe a couple more that escape my memory at the moment.