adwsystems:
Interesting. Are there specs anywhere available on how well each color works in that regard?
I thought, you were just interrested to get three states...
Regarding the color response, expect a LED to be sensible in it's own color, specially those with colored encasing.
The blue ones should be closer to the spectrum of solar panels. The fun thing is, that you can put them in series, mix colors -even reversing- to design your very own color response. 
But, the output is quite variable from one diode to the other, so it's not a solution for production.
But you just need a couple of diodes and a multimeter to get your own experience...