I have two B-17 specials and both leave brown stains on lighter riding shorts.
I have proofhided several times and used various leather cleaners in an attempt to stop the leather dye from transferring to clothing. Wonder if any other Brooks owners have this problem or if they just ride in black shorts. As to the comfort of the saddle, it's great.
I always figured that's why God made bike shorts black...
I have a couple of brown B-17s, too, and I haven't noticed any transfer the few times I've ridden in light-colored street shorts. That would be all short trips, though, so maybe I'm not giving the dye a fair shot.
I have no idea if this will work, but how about giving them a good washdown with saddle soap, rinsing well and then Proofhiding them after they dry? Shouldn't hurt them if you don't ride them wet (mine have been soaked several times) and let them dry at room temp. DON'T use a hair dryer or any other heat source to hasten the drying, though.
Two things come to mind. You might check out Sheldon Brown for tips and you
can also check out www.wallbike.com. If that doesn't help then I would
just send a note to Bill Laine at WallBike. He is a terrific source.