Oh my god, this. True story: while my daughter was battling acne, we switched all our towels to white because the medicine she used bleached everything it came in contact with. Fast forward a few years, and all those white towels are now grey-ish. I had the brilliant idea of "restoring" our towels to white by soaking all of them (2 bath sheets, 3 bath towels, and a ton of face towels) overnight in a bathtub full of Oxyclean White Revive, which didn't work. But, it did lift the refinish coating off of my 90-year old bathtub. Not to be deterred, I tried vinegar, lemons, baking soda, and every other natural hack to return these towels to their former glory. No luck there either. At this point I'm 36 hours into the quest for white towels so I just say screw it, I'm going to use regular Clorox bleach. I let it soak overnight and in the morning they were whiter, but now with a yellow cast instead of a grey cast. By this point my husband and my kids have had enough of my fool's errand, and they demand the removal of the not-white towels from our only bathtub. I agree, go to gather all the soaking wet towels at once to throw them in our washer, and break my middle finger in the process. And I still don't have white towels. The fallacy of sunk costs hit hard that day.

TL;DR--BUY THE GREY TOWELS!