Originally Posted by
dwainedibbly
If I recall, and I may very well be wrong, using a red LED will be more efficient than using a white LED with a red lens because a white LED is actually putting out infrared with a phosphor that glows white when the IR light hits it. That isn't a 100% conversion. Then some of that light gets filtered out by the lens.
I'm not certain how white LEDs work; I had assumed it was an RGB combination that looks white to our visual system, but maybe it's what you describe. In either case, the red lens would block (i.e. absorb, i.e. waste the energy from) the non-red components of the light. Thus, most of the light energy goes into heating up the lens, whereas all of the light energy from the red LED is useful as, well, red light. I think the white LEDs are somewhat more efficient at converting electricity to light, but I doubt this makes up for the inefficiency of blocking most of the light.