whats this bluing stuff that gets the yellow out of whites called.??!!?

I'm not sure how this question ended up under dental, but you are looking for Mrs. Stewart's Liquid Blueing. It's designed to counteract the yellow left behind from Chlorine bleach. It is simply a colorant and doesn't bleach. I use it on my whites. Read instructions carefully or you'll end up with blue Vans

oddly enough the "blueing stuff" is called blueing liquid, go figure lol. You can prob. get it at walmart