You can buy replacement unactiviated stickers on e-bay from people like this

http://shop.ebay.com/toyoman8710/m.html

for $2 if you need to replace it.

It doesn't take that much to get them to change color, high humidity will do it on some.

It has also been suggested that you can change it back to white with a drop of bleach on the sticker, see this website for pictures:

http://www.instructables.com/id/Turn...Wetquot-Indic/

L