Some users have found that their cup becomes a little stained after a number of uses, it seems that the discoloration is related to the hormones and the unique natural chemical balance of each person's vaginal fluids – some people notice staining and others don’t. 

 Don’t worry if your cup becomes a little discolored. Washing with lemon juice can sometimes help remove stains as can allowing your cup to sit in the sun for a few hours.