I'm so sick rn, so gonna drop some sick headcanons for Color Spectrum Duo.
Under Nightmare or Chara he always pushed himself through the sickness until he literally collapsed
I think fever would destabilize monster's magic, and there is no better reminder than it for Killer that he's still a monster at his core. Because it happened more than once that he accidentally teleported into the Void while sick
With Color, since his bestie gets upset if he works/does chores when sick he does the next best thing (in his mind) and hides in his wardrobe until the 'danger' is gone
If Delta is over for a visit he's surprisingly clingy with him. He's exclusively clingy with him when he's sick. And it's literally just because Delta registers as the biggest threat in the group, so if he's around him he's untouchable by anyone else
Horror, Dust, and Cross have never once seen him sick, he made sure of that. Because he needed to be the untouchable one between them so they didn't think they could ever do something stupid like running away while he was in charge. It didn't work too well with Dust or Cross, but it worked like a charm for Horror
Killer is usually the one doing most house chores between him and Color, and Color at times has to physically restrain him from doing them when he starts noticing him getting sick (he always notices before Killer. He has 6 kids to take care of, he has a sixth sense for that shit). Killer is the most stubborn about cooking (that's mainly because he likes it, but he'll never admit that)
If you think that Color is any better at handling his sicknesses than Killer you're seriously mistaken. He's a parent to the core, his anxiety shoots through the roof if he's unable for whatever reason to take care of others
Killer usually calls over Delta and Epic to take care of him when he's in that state (Cross often tags along) because he has no clue of how to help
His fires get actually hot and dangerous when he's running a fever because his magic goes haywire too. So, as cuddly and clingy as he feels, he can't hug others and that's truly the worst thing
While in the Void he never was suck, so he often associates dark spaces with recovery while ill, so taking care of him often turns into a game of hide and seek
The younger souls get anxious when he's sick, a good way to keep them calm is putting on some cartoons or playing some light-hearted music. Keeping them calm is vital to avoid Color's dad mode from kicking in
Color is the one who gets sick the most among the extended chromatic crew because of his pre-existent physical issues. This does mean that his buddies are the most used to taking care of him, but it also worries them immensely and it means they're often overly careful with him (to the point that he often has to tell them to knock it off)
It sucks to be sick, I hope you’re able to feel better soon! 🙏 🫂
Killer lingering around Delta more than usual must be the biggest sign that bro isn’t feeling well 🙏. Delta probably gotta wrestle bro into resting.
Color getting anxious because he can’t basically hen over someone now feels canon to me 💀. Bro always gotta be moving, always gotta be doing something for someone. I’m very curious to know how “hide and seek” when Color’s sick goes down. Also love the idea that he finds comfort in the dark and dark places when sick, precisely because he never got sick in the Void.
And given that Killer hums to himself canonically, and Integrity is associated with music via those eighth notes, maybe Killer hums and whistles while he does some chores or work nearby and Integrity sings the lyrics for Color and the younger souls when Color is sick.