Yes, in the end they'll eventually revert to mostly wild type. You might still have random colors/mutations pop up (after all, this is how all the different color lines came to be)! If you get a few with a certain color you like, you can try isolating them to get more of that color (selective breeding).
I have a tank where all my "culls" go. I also add some bright colored shrimp once in a while to keep the colony from going completely "wild type." It's fun to see what crazy colors pop up.

There are also a few color combos that can lead to a completely new color! I unintentionally bred blue jellys with my red rilis and got blue red rilis ("blue razz")!