i dont know much, but i know a little bit. What is the volts of the blue led that u want. Im pretty sure that if u have a 5v one, u shouldnt need any resistors. You just need to find the 5v lead from the mouse cord. If you have a 3v blue led, then u need a resistor that will cut the power down to around 3v. Anyone else that knows something about electronics want to help. Other ppl have posted similar questions to this one before, i think.
Xxcr4shxX: what ever
Crash2108: no, tell me what w/e is first