What Causes Greenish Discharge From Nipple?

my brothers girlfriend just called and asked if ive ever experienced it before but she sayed ... she had squeezed her nipple and some type of liquid ame out of it...she sayed it was a greenish color it think but my brother sayed it looked blueish... shes on birth control..she gets the shot and shes not due back till june 16th or something.... is this normal or whats going on with her