It means the dye isn't color fast. It comes out of the fibers and stains when it gets wet. Like when you launder a new red shirt with the whites by accident, and everything else turns pink. Surely all red materials aren't like that, though?

I have some red marabou and hackle, but I just started tying and haven't used them yet. I did use red chenille on a jig body, but it's more of a rusty red. I have had a lot of success with a red headed jig with a plastic grub, though. I use the Harbor Freight red powder paint.