I encountered a theory I thought you might like: when two trolls join together in moirailegence, the lower-blooded troll will often wear something of their moirail's blood colour to signify to threatening higher-blooded trolls "If you kill me, this is what will come after you." It would explain why Nepeta's tail and cap are blue. Thoughts?
I actually really like this theory! I’ve seen it applied in a few fics before, and I like seeing little touches like that included in fanart. I’m also a big sap, and I absolutely love this headcanon applied to all castes and blood colors. It’s sorta like the concept of a friendship bracelet that way. Plus, come on, who doesn’t love the idea that Nepeta gives Equius little paw print themed charms?