Your breasts change in preparation for breastfeeding. By month three, you may notice your nipples and the area around them (areolas) are darker. This is from hormone changes that affect the skin's pigmentation. The freckles and moles on your body may be darker, too.
Your nipple may stick out more and the areolas may get bigger. Also, small glands around the nipples become raised. These glands produce oil to keep your nipples soft. All these changes make it easier for your baby to find and latch onto your nipples for breastfeeding.