Hi.
I really have no idea to what you're referring. However, I can tell you that if someone bites your lips or kisses them hard, they may bruise--just as would happen with any part of your body. I've never heard about other potentially more serious problems due to purple lips. That's a new one on me.
However, if you're truly concerned about this, and your lips don't heal in a few days, please see your physician to find out what's going on. Dr. J
Here is a picture btw, of what I am talking about. The majorty of the middle of my bottom lip is clearly darker than the rest (in real life, it looks totally purple).
It may feel strange as well, but I can't tell. May just be a mind-thing/paranoia...
Oops, here was the picture
http://blake.comoj.com/images/lips/lips.jpg