From: "Eric Smith" <eric(a)brouhaha.com> Doug Jackson wrote: [...] Blue LEDs don't require any phosphor. The phosphors are used to get *other* colors from blue or UV LEDs, such as white. Agilent made some really nice white LEDs that didn't have the remaining blue tint of the common ones, but they were expensive and no one wanted to pay the premium, so they've been discontinued. The earliest blue LEDs (Silicon Carbide) had very low output, so RGB LEDs needed two blue dice to one each red and green to get decent matching. However, so much R&D has been done to improve them that now blue LEDs (gallium nitride) are now the *most* efficient, at least in the visible spectrum.