In addition to bad breath and teeth staining, smoking can darken lip color visibly. Smoking can greatly increase dehydration of the lips, and thus contribute to it's darkened tone. By taking care of your lips and using the appropriate preventative measures, you can save your lips from discoloration.
Wash your face. A clean set of lips is best for putting on any topical treatment for the lips.
Rub lemon juice on the lips in the morning and rinse after one minute. Lemon juice is a natural skin brightener and a good preventative measure for smokers who wish to retain a brighter lip color.
Apply lip balm to the lips. The lip balm should contain at least an Spf of 15. Spf in lip balm will help prevent discoloration also.
Spread clarified butter on your lips in the evening before bed. Clarified butter has plenty of moisture and is a good aid for smokers who wish to prevent darkening of lips. After rubbing lemon juice on your lips in the morning, and clarified butter at night, you will have formed a decent preventative routine to ward off darkening lip color.
Tips
Drink at least 10 8-ounce glasses of water per day to avoid dehydration.
References