Mine was still yellow and thick- so colostrum mixed milk- until about day 6 or 7 but there was lots of it by then and i could express lots. I felt the feverishness/swelling of my milk properly coming in late the night of day 4. I was BF then expressing up hurry my supply up because DD was too sleepy to feed properly and hadn't gained the desired amount of her birthweight by day 3 (10%). Which I might add is one of the stupidest hospital guidelines. How many women's milk has really come in by day 3 and why weigh the baby on that day of all days? Anyway I digress...