Early on I had some burgundy bleed and ruin corners on a quilt. I always wash fabric as soon as it comes in. If I want it stiff again, I'll starch it. Occassionally, I will get charm packs and just rinse them in the sink. If a piece is miscut or looks like it may ravel, I'll put it in a lingerie bag before washing.
Anyone who doubts that colors run should use a color catcher just once. There are tons of loose color that may not streak, but could leave your colors drab.