[Lucid:]

Ninfia is the lightest Eeveelution.

:O

That said, it just doesn't look like "light" to me. If the coloring was more prismatic, I could see it, but pink with a few blue spots doesn't seem like light to me. But it doesn't look like fighting, dragon, ghost, or any other type either.
Also, if they were introducing sound types as well, I would think there would be an eeveelution for both sound and light, not just one of them. But maybe there's another eeveelution or maybe it's only one new type. Who knows.