Beautiful mutt guppies that I want to line breed with

Their body has beautiful pink iridescence but not showing here on the photos. I bought their mom, a beautiful yellow cobra from lfs and she gave birth to them. I believe they had an endler dad cause I remember seeing some pink endlers in the same tank. I have 4 males and 5 females from this batch, and more fries are growing up.

I want to line breed them and creat a pink guppy strain. Any suggestions/directions on the best route for a healthy and stable strain? Thanks in advance!