These might've been brought up here before, but then they might've not, so:
Firstly, Remilia's theme, Septette for the Dead Princess, ties into the next game in the series in a few ways.
One definition of Septette is "a group of seven people playing music or singing together". PCB is the seventh installment in the series, and there are seven bosses/dialogue-possessing opponents (Letty, Chen, Alice, the three Prismrivers, and Youmu) before the boss of the game, Yuyuko, who is a ghost and the princess of the Netherworld, nicely tying up the rest of the name.
Secondly, Yukari, according to the wiki, "means 'purple' or 'violet' (In ordinary Japanese perspective these two colors are not discriminated)".
However, spectral violet and composite purple are two very different things; violet is a true colour, a single wavelength of light producing a shade closer to dark blue than purple, the latter of which being a composite colour consisting of both red and violet.
So if you interpret Yukari as "purple" instead of the the spectral blue-ish violet, then instead of her name representing the high-energy border of the visible spectrum, it represents the combination of both of the colours making the borders of visible light. (Incidentally her PCB dress seems more purple than violet, so that could count regardless of which colour you choose to associate with her name.)
