Computer_Commando's comments ring true. My Case has Blue LEDs in it for whatever reason- if I wanted them to be red (again, for whatever reason) I couldn't just rip out the red LED from my old cases or floppy drives- different coloured LEDs almost always have different electrical requirements- often just changing a led from one colour to another requires a resistor or two (or the removal of resistors already present), and in order to know what you need to add or remove you need to know the exact specifications of both LEDs and then you have to do some sort of math to come up with what you need to add or remove.
