BO, I tried the egg yolk paste but it over-clouded my water and spoiled it too quickly. but it is a good food source for 'em! I just didn't want to be cleaning my tanks *that* frequantly... I already clean them every other day.
daryl, with my one that is showing her color, it started showing up at around 3 or 4 weeks. But it does vary depending on healthy, temperature, feeding ect.
A lot of mine are different sizes too. And I noticed that some from this new batch have a golden cast to their body, while others have a blue cast. So these are definitely the babies of the Japanese Neon Blues! I thought they had managed to mate with her before they died off on me.

At least I got a little rainbow after the storm (in the form of 21 new fry).
I'm up to 50+ guppies right now.

I think I may stick an ad in the local paper for the non-doubletail babies. I really should be making room for these guys since they are the main focus of my project.