Wireless Controller IR LED

[wolfman]

I already posted in the PCE/Supergrafx section, unfortunately no answer there...
Maybe someone here knows that?

What is the right wavelength for the IR LEDs in the controllers? I´d like to replace them since they seem to have weakened, but since there are several different wavelenghts available (actually the LEDs are dark mauve-coloured), I am not sure which ones to buy...

Thanks for any hint!