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.

Having written that, I think I might have read it on the Dinotte site somewhere but I'm too lazy to look.