I've really just gotten the guppies I have now from an LFS a couple months ago (I am NEVER going to Petco for fish EVER again!), and it looks like the female I got was impregnated by a yellow male; the kids are just coloring and I can see the yellow and black in their tails and fins! I'm personally looking on Aquabid.com and in my area for purple guppies, just to try and start my own strain with a mix of yellow and purple coloration. Theoretically, the two opposing colors should strike out, making the future guppies aesthetically pleasing.