While spring cleaning I found a box of mostly RS232 mice, before binning
them I decided to harvest any phototransistors/photodiodes/LEDs.

A very old optical mouse had 2 LEDs and a 4 quadrant photodiode - one LED
was water clear, the other was tinted almost cyan colour.

Does anyone know the significance of one LED being tinted light blue? As
they are just the same as any 5mm moulded LEDs, there is obviously no part
number marking I can search for data sheets.

TIA.