Change the order in legend & color of photon

[DianaTavares]

From September 9 design meeting:

Reorder to proton, electron, photon. “Photon” and “proton” look a bit similar, especially next to each other.

If we change the color of the electron to blue (issue #60), make the photon in the key yellow/green so that the electron and photon look more distinct.

[pixelzoom]

The original order was from smallest to largest particle. And "proton" and "photon" only look similar in English. But I'll proceed with this change.

The legend has been reordered, and the photon icon is now 530 nm. See screenshots below. @DianaTavares please review, close if OK. If you'd like a different color for the photon, please tell me the wavelength to use, and make sure the color works for Projector Mode.

[DianaTavares]

The idea of the green was to better distinguish between the electron and the photon in the legend now that the electron is a lighter color. Green looks like a good idea, but I don't like that I can't see the “star” in the center (as all the photons have).
I like how this purple looks like in back and white background:

and it is the 410 nm

[pixelzoom]

Photon icon is now 410 nm, screenshots below. Back to @DianaTavares for review, close if OK.

[DianaTavares]

Perfect! Thanks!!!