Baby poo!

My son is almost 6 weeks old and before this week he was having very yellow bowl movements. Which is normal for a breast fed baby! But this week they have become more green (slight green tint)! I have been making sure that he is draining my breasts but I wonder if my pumping has impacted something! Or maybe I'm not eating enough. He has the same amount of wet diapers and soiled diapers. He is very alert and does not have a temperature! Anyone know what's going on?