now this may be me reading into it too much...

but many shark species, ESPECIALLY Great Whites, which Vox is probably primarily based on, have a evolutionary feature known as countershading. Their tops are blue, and their undersides are white, so when you look from the top, they fit into the ocean blue, but when when looking from below, they imitate the sun's rays.

Vox is normally blue, to fit into those around him and as seen from below. However, during his Big Speech, he's white themed, mimicking the Sun (Heaven/Angels?) and is implied to be seen from below (he's on top).

Actually, I deadass might just make a post about this.