Yep - it's so production and assembly can tell what colour light output it will have. For example: White/Blue/Green/Red/Yellow-Green/IR etc
Some people remove the stickers (I do).
One person here on CPF I saw puts appropriately coloured and sized rubber bands onto the flashlights to tell them apart in use. For example the bezels of the L1 and KL1 have a "channel" that can be used to locate the rubber band. Pretty cool idea if you have several different colour output versions.
Al