ninjabear: To be honest
I haven't seen the inside of the mobile that has a sticker or anything that changes color.I doubt it is a sticker there's just no room for it.Everything is tight inside.The sticker might cause problems to the hardware
They are usually small 'white' stickers, they might have red dots on them. Usually there will be one in the battery area and one inside the phone itself.
They aren't big, but will turn red and there will be a bit of red ink inside the phone - a sure sign of water damage.