First, I overcast or serge the raw edges of new fabrics.
I soak like colors together in hot water in pots and pans - or buckets. Basically, if one of them has bad manners, it won't hurt the other pieces.
If, for example, I find that the green pot has green water, then I will go through the fabrics piece by piece to find the culprit.
The culprit will get additional rinses until the water barely turns color.
My DH isn't real thrilled when he finds pots all over the kitchen when I'm soaking fabrics, but - oh, well.
Then, after I'm reasonably sure that they will play nicely together, I run them all together through a very short, gentle cycle in cold or tepid water.
After all, when after a quilt is made, all the colors have to get washed together at the same time.
I prefer to dry the pieces in a dryer, but line or rack drying also works. When line drying, I try to fold the selvages together and pin the selvage edges to the line. I hope that doing it that way will minimize distortion and stretching of the fabric.
I've only run into several pieces that were bleeders that never stopped coloring the water. (This is over about 40 years of fabric accumulation).
One was orange, one was dark blue, one was turquoise, one was purple. And I think there may have been a green one.
We have a septic system - so the water output does matter. DH grew up in a house where water was carried in - and the used water was carried out - one does become very aware of water usage when that is the case.
DGDs were living with us for a while - DH practically went ballistic if all he found in the dryer was one pair of thong underwear. :roll: