This problem is the only reason I finally switched to lycra shorts. I think it's possible to dye wool so it won't bleed, because this never happened to me in the first twenty years of wearing them, but then it did, ruining a really nice white summer weight wool jersey that I was very fond of. At that point it was getting hard to find good shorts and I gave up.
I sort of remember learning somewhere that salt can affect this. That may work either way--maybe that's what caused the dye to bleed in the first place (sweat), but it wouldn't hurt to try soaking them in a salt water solution to see what happens.
By the way, I recommend using Ivory soap for wool stuff. It is much gentler than Woolite. You should also hang wool to dry vertically from a hanger to discourage shrinking. In my many years--I still use wool jerseys regularly and still have some that are almost 40 years old--I've tried everything. You can use a washing machine--cold water, most gentle cycle, hang dry. Ivory, either in liquid or flakes for the soap.
Hope this is of some help,
Bob Schenker
Oakland, CA USA