I've got a real Brooks in black, and it has left some stains on some of my pants. I've got one pair of khaki shorts (made of nylon, though, not cotton) that has a distinct black stain through the crotch in roughly the shape of a chamois. But I think that I have finally worn through the bleed-off and shouldn't get any more stains. My saddle is a couple of years old. That pair of shorts with the pronounced stain got stained right after I got the saddle--it was still new and wearing through its first proofing. Next time I break in a Brooks, I'll know to conduct a few long rides in old jeans before wearing nice pants on it.

Maybe someone needs to create cycling shorts with an exterior chamois made from a buffing material. I'm pretty sure there's not a lot of market competition for that product.