When dust is smaller than or comparable to the wavelength of light, the reflected color is dominated by particle size effects rather than the intrinsic color of the material.

For X-rays, the phenomenon of diffraction by crystals was a natural consequence of the idea that X-rays are waves analogous to light and differ from it only by having a smaller wavelength.

This model can be transferred directly to what we now see in Uranus, although we still need to understand the details of the process.

We went out in October to image both rings and we simply couldn't see the outer one. We should have easily seen it if it was a normal ring. The interesting part was that the outer ring was the one that was the brighter one in the Hubble images.

I think there is no chance that the blue ring is caused by geyser activity. We don't know what the composition of the particles is.

It's funny that this research got started by something we didn't see.