Hmmm... So I guess 5mm red LED would be a better option. Saves me the trouble of having to machine a replacement piece for the colour filter housing. I use the red filter most of the time anyway.
Red is so common and I think I have some lying around somewhere.
Found this website.http://edusite10.tripod.com/led3/bulb/index.html
Thanks for your help and the links.
I think I better read up on this stuff to get some background knowledge before using white LEDs...