actually, i just took my purple sharpie here at work to color the blue LED.. and nothing happened. i swear that i did it in the right spot described, but then again, you're talking to the one who was dismantling the batt end of a carto to try to refill! 
so.. i'll try again when home. it's VERY VERY VERY tiny, where the LED "is" (or, where i thought it was)

so.. i'll try again when home. it's VERY VERY VERY tiny, where the LED "is" (or, where i thought it was)