led A button mod, how many volts for blue resistor, resistor used?

[lowriders715]

i understnad how to put led's in, but i wanted to know how many volts does a blue led require on these wiimotes, as blue led's range from 3.0 v to 3.5 v... also since two AA's are in the wiimote isnt that 3.0v? so is it nessecary to put a resistor.... HAS ANY ONE PUT A RESISOTR as it will save batter life, but how much exactly? how many ohm resistor? ALSO, does a blue led really drain the battery life out of the wiimote, what size of led should i use, anything lower then 3mm?