LED size

[frizzen]

I'll run 3mm or 5mm pretty interchangibly depending on what the body needs. Sometimes you may need to put it in a lens bezel or something.

If you get into surface mount leds, the pre-wired ones are easier to deal with.

A White led can kind of wash out how your red lens to more of a pink, but so can a bright Red led. You can balance that with translucent red paint, or dimming the led with more resistance.
I prefer to run a Red led where i want red, Yellow where i want yellow. That way it's not a blue led filtered to white, shining through a red lens.

Some colored leds are Clear, if it'll be exposed i'd probably paint with something like tamiya Translucent Red, unless i just wanted something looking Altezza style