Definitely synthrapol. But do a Google search. Someone did a test and found that Dawn original worked as well without the color fading that synthrapol causes. I will post the link I'm talking about if I find it. I suspect that Palmolive original would work similarly.
The idea is to wash with SOAP and not laundry detergent. The main ingredient in powdered laundry detergent is soda ash. Soda ash helps colors ADHERE to fibers, and technically it could set any stain. Definitely don't wash in laundry detergent until you know the colors won't run or are finished running.
My own experience...as long as I didn't dry in the dryer or wash in hot water, if the color bled, the bleeding would come out.
When colors bled, I treated the area of bleeding and the offending fabric with synthrapol, let sit for a few minutes, then wash in synthrapol. Sometimes I had to do this more than once, but I didn't dry until I was sure there were no bleeders and all the bloody mess had come out.
I've had terrible bleeders even in the realm of "good fabric". As far as I'm concerned, you can't trust any manufacturer to not have bleeding fabric.
Oh, BTW, people also swear by those Shout color catchers, so definitely get some of those to wash with your red quilt.