Your asking what would happen if you put a yellow that had blue pearl parent in with regular yellow? Your yellows genetic diversity would go up a bit which is generally a good thing. However, your yellows would probably start to throw some random blues... which is generally not a good thing. Might effect the yellows color in a bad way too.
If you have both yellows and blue pearls already, I think its more likely that a micro baby hitched a ride on a net or plant or water or rock, etc, into your BP tank. There isen't really anything constructive you can do with it if it is a spontanious mutation. If your convinced it is from the BPs, and you wanted to try something fun though, you could move it with some BPs into their own tank and try and get more yellow F1s, then at that point you could take out the BPs and leave only your home breed yellows in their own tank.
Theoretically you could keep culling the blue offspring and keep the yellows and after a number of generations you might have yellows that breed true again. Most likely they would be %99.9 the same as your other yellows that you bought, but at that point you would have your own "strain" of yellows. Then when strains of yellow are cross breed back, it would increase the genetic diversity and therefore the hardyness of those yellows.
It would be alot of work for not much of a result, especially considering yellows arn't known for being heavily inbreed already, so they dont need bump in diversity... If we were talking CRS though, now theres a variety that could use a bump in diversity.