Why does "pink belly" even happen?

[BHReptiles]

Hah, so maybe I just don't see enough white snakes in shed.

-Jen

At first we thought the snake had dye on it (from the colored bedding it was on) but the bedding was blue and the snake was pink! There was another snake in there with it that was also an all white snake and it was not bright pink, thus why we thought the snake might be in shed. That's not very scientific, but it's what I can remember.