You betcha I pre-wash. Everything. Like colors go together in the washer, and anything that's a medium value or darker goes in with a color catcher. I repeat the washes with additional color catchers until they pick up very little. I recently used a red next to white in a quilt and was horrified when the red dye ran onto the white when moistened by the glue basting. Fortunately it all came out once I washed the completed quilt -- with, yes, a color catcher.