a personal hc of mine (which slowly has spread to other people. hoho.) is that coil's horn change color depending on what he's feeling. you probably noticed it on some of the drawings i made, but generally, it's like this :
grav/blue : "main" color. you'd see this most of the time, and very rarely you see it change if you're not familiar with him, or just mere acquaintances. here, he's confident, smug, very typical coil. though, it's also part masking— because coil rarely (if ever, but thats up to his own character development) gets closer to other people, he is playing up his persona, hiding what he's actually like. yknow, putting up the facade that we're supposed to dismantle.
speed/red : a burst of strong emotion. could be anger, flustered, or....gasp....love?! not much explanation on this one. though, in my mind, it "shows up" very quickly, like its namesake. unless you're paying attention, you might miss it.
regen/green : this one is the most hc loaded of them all (like im not making bullshit up at this point) but regen coil is "true" coil. much quieter, calmer, analytical. i tend to depict regen coil when he's experimenting, or on his lonesome. very very few people (read : skateboard and/or boombox) has seen coil like this outside of healing context, and most people would probably be surprised seeing him like this since its such a 180 from his usual attitude. also, this is indulgent, but i like to pair regen coil with glasses.
