Should I prewash red sock yarn before knitting with a contrast yarn?

[Phaedra]

Hi,
I've been requested to make a pair of red socks with yellow toes and heels. The chosen yarn is to be Blue Moon's STR in the Brick colorway with a Hoofle Floofle toe and heel.
When I did a pair of Brick last year and washed/blocked them, the water stained red. And I afraid I'll end up with orange toes/heels. So, is it advisable to prewash the Brick skeins? Can I set the color somehow? Do I use a color magnet? This is going to be an expensive pair of socks: I need 2 skeins of Brick and 1 of the yellow. Any help would be welcomed.

[mwhite]

YES! I would throw a sheet of "Color Catcher" (made by Shout) in with it when it's done and washed as well.