I don't prewash. Anything. Ever. One of the things I have figured out in out in doing laundry for the last 40 years is the bleeding issues. I've only ever had *1* thing pick up and keep a dye bleed in 40 years of doing laundry. One. And I managed that *with* bleach.
Here's my challenge, do a load of your normal laundry. Be brave, mix a couple of dark or even red tops in there with a bra or maybe something else light in color. Make sure they're things that you've had for at least 6 months. Then do the exact same load with a color catcher.