>  The main problem with "white" leds is that they are not white. They emit
> a set of very narrow frequency spectra, which might fool the eye to 
> believe
> it's white, but since it's not, it kills colors.

Yes, that's described by the CRI as I mentioned in another post, it's not 
quite as bad as you make out, usually the same as the CFL lights.  This 
chart shows the spectra of a typical white LED compared to a normal light 
bulb:

http://www.professorled.com/e/par16/sad.jpg

The CRI is typically around 70 for a white LED like that, compared to 0 for 
monochromatic sources, and 100 for an incandescent light bulb:

http://en.wikipedia.org/wiki/Color_rendering_index#Typical_values

If you want higher CRI with LEDs it's relatively easy to add green and red 
LEDs and then you can achieve near 100% CRI, actually this is what we do in 
our LCD backlights for certain customers who demand very high quality 
colours.

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