A friend inquired of me---she has discovered a dated quilt top that was in her family. Somewhere along the way it was laundered and the red bled into neighboring blocks. Can that be removed now by using a color catcher or is it there for posteriity?
Any advice out there?

It would depend on the age of the quilt. It would help to know the age of the quilt, laundering is hard on older fabrics. If it is not too noticeable I probably would not wash. Others will weigh in with more advice.

I would soak it in Oxyclean then wash it on gentle with lots of water so it's not crowded. I think Color Catchers only pick dye from the water, not the fabric.

There is a product (i think by Rit) that is specifically for getting color bleeding out after the fact....not the color catchers. It is in the laundry dept of most big groceries.

The red may eventually come out if she washes the quilt repeatedly in Synthrapol. Synthrapol suspends unset dye particles in water so they rinse away instead of settling into other fabric. I use it the first time I wash any quilt, and continue using it if I notice any color in the wash water. It would have helped prevent the red settling into the other fabrics during the original washing.

Even now, though, if the bleed has not been permanently set (by heat, by age, etc.), Synthrapol is likely to gradually lift it out. It would be worth maybe 2 washings to see if there is an improvement or not; if there is, then additional washings are in order.

These multiple washings are somewhat hard on a quilt. If it's a really old quilt, I might hesitate to try it.

Synthrapol is widely available online from Dharma Trading, ProChem, Amazon, etc. Quilt shops that cater to home dyers also often carry it.

I made a rag quilt that had red flannel in it and the dye ran and turned the light blue parts pink! not good for a two year old little boy! Anyway one day at Joann's i saw some stuff made by carbona that said it would remove the dye runoff. I used it once and all the pink disappeared. I was amazed. i just looked it is called color run remover. i think you could find it stores by the laundry supplies