What does colostrum look like before birth?

I'm curious because ever since I got pregnant the one thing I never understand was where the milk came from. I looked and looked and couldn't mind the holes or anything (I felt dumb afterwards I know). Well now I'm 30 weeks and my original C's have turned into DDD's. Along with that my chest has this clear liquid stuff but its very very little. I always though colostrum was thick, before birth is it clear? and does it change colors after a while cuz sometimes if the liquid dries it turns into a whitish thing that looks like the crusty off of milk cartons.