I photographed the new white street lights that they have been putting up around Wigton. I used a diffraction grating thinking they were mercury vapour lines and that I'd get an interesting emission spectrum. I got an almost continuous spectrum. It turns out that they are white LEDs. There are two spectra in the photograph above. The top one is the full Moon. The lower one is for the LED street light. Note that it has a gap between green and indigo/violet. If you look at the spectral intensity graph on this webpage, you'll see that we should expect a gap at about 500nm which seems about right
http://rsos.royalsocietypublishing.org/content/2/8/150291
