A Theory on Moiraillegiance
It’s already been stated that Eridan and Nepeta wear their moirails colors
Eridan’s rings (back when he and fef were moirails)
and nepeta’s hat, tail and shoes
Now the question is why? Why do these two wear their partners colors, while Feferi and Equius do not? What Nepeta and Eridan have in common is both Eridan and Nepeta are lower on the Hemo-spectrum than Equius and Feferi.
Here is my theory. The moirail with lower blood will wear the highblood’s color, not out of devotion, but for protection.
We all know Alternia is a pretty violent place, and there is no consequence for a highblood killing a lowblood. We also know that moiraillegiance serves as a means for soothing and controlling highbloods who would otherwise be dangerous. AND we know that moirails can be extremely vengeful when their parnter is killed.
So in order to prevent accidentally killing a highblood’s moirail and setting them off on a murderous rampage, the lowblood wears the highblood’s color to show they are “taken”.
Eridan doesnt wear as much pink. He is a seadweller, and immune to most hemo-spectrum related killings. However, his moirail is the Heiress, and pretty damn important, so it thus marks his importance as her moirail. It also warns his potential killer that they have the wrath of the heiress on them if they were to actually kill him.
Nepeta on the other hand, wears a whole lot of blue. Since she is practically a lowblood, she needs to make it pretty clear that she’s under the protection of a blue-blood.
So basically, wearing your moirail’s color is a warning sign. Equius and Feferi allow Eridan and Nepeta to wear their blood colors as a “bitch step off this is mine” sign to people who might want to hurt them.