Pink and Red usually means corruption.
I'd personally put it as just pink normally, because- within the context: shapes are usually colorful, which represents individuality, but the corruption sort of 'negates' their colorfulness by making it just one color for everyone :]
Which is also the reason I don't put JUST their colors in the text, but also their names when the characters are talking WITHIN the story.
I sort of have a system for this kind of thing: usually, when it's within the story, I put the name of the character before the dialog, then color the dialog in that character's designated color(s), like- sometimes colors may repeat (e.g.: both Hethagon and Fern are green, but due to Fern being a hero, I make it half green half white, while Hethagon is JUST green), and that represents their individualities; when it's outside of the story, I put just their colors because I designated them as such, and no side characters are supposed to be in the ask blog outside of the story, so you can tell characters apart from each other easily (so much so that it's in the introduction post, to make it easier)
The corrupted counterparts of the characters are going to appear outside the story at some point (like the Cubic takeover in the Cube ask blog), so I might as well explain the difference here too- outside the story (takeover version): Hethagon, Hexatrix; Cube, Cubic; Rubi, Rubix; Zulu (normal), Zulu (corrupted); but inside the story, they're all gonna be entirely pink (except for Zulu, who will follow the one I put above).
So, in summary, it all boils down to the fact the corruption rips a character of their individuality to make them pink... if that didn't make much sense, feel free to ask me again :,)