blue seat?

So this is so weird and I'm kinda embarrassed but... recently I've burn turning toilet seats blue! Seriously, blue. I noticed it happening on my toilet seat a week ago but I thought maybe my sister came home drunk and sat on the seat with her jeans, until I spent a few days at a friends house and now her toilet is turning blue! So is the bathroom seat at my job! I know I'm doing it. I don't wear jeans and I'm not pregnant. Does this happen to anyone else????