Most blue LED's are 3v+ And they can become EXTREMLY expensive if you go with the brighter ones... Best bet, buy a new mouse with a blue LED in it, and chances are, your photo sensor won't pick up anything if you change the color... That and the surface mount resistor they use for the red LED may not let enough amperage through to power the blue, or it may (I seriously doubt this) let to much through... And 3 blue LEDS in your keyboard, won't fry a PSU, it would fry the keyboard/USB/PS2 ports. Only way they would have fried the PSU is if your stupid, didn't know what you was doing and hooked them straight to it, even then, if you used the correct resistor it wouldn't have killed it.... BTW, learn OHMs law....