Okay, this stuff is AMAZING! DIY shower cleaner -- vinegar and dish detergent. Don't worry about the brand or color. We used clear store brand detergent and it was GREAT! NO SCRUBBING required. As long as you can tolerate the smell :)
Goodbye to Yellow Armpit Stains: one part Dawn dishwashing liquid + two parts hydrogen peroxide + some baking soda. Use a small laundry brush to work the mixture into the stain for a few minutes. Let sit for an hour or so then launder as usual.