When I was about 18 weeks colostrum started leaking out of mine in small amounts. It's been increasing as the days have gone by but it only happens every once in awhile...and colostrum is clear and milk is sort of yellow when it first comes I've heard :)

what's the difference between colostrum and milk ? when it comes out

I'm 29 weeks and have been leaking colostrum for about 3 weeks now

About 2-3 days after delivering but you will leak colostrum (the clear stuff) anywhere between 30-40 weeks pregnant.