I agree Newt. PUR-efficiency is a better way of comparing how much photosynthetic "power" you get for the electricity bill.
The standard measure that quantifies the energy available for photosynthesis is "Photosynthetic Active Radiation" (aka "Photosynthetic Available Radiation") or PAR. This is blue and red light.
PAR is everything between 400-700, so that contains green too.
PUR is PAR too, but weighted towards a general photosynthetic action spectrum - which limits the importance of green and yellow.
Aqua Botanic-light bulb comparison