they’ve got a really fun design! how would they communicate and work together in a combat encounter?

The build i was going to run was hexblade warlock
HOLD HOLD ON THERES A NARRATIVE REASON I SWEAR
So Chell, the white half, was a fighter, and they were pretty physically adept, Zo, the blue half, was a magic jeweler
so invocations? Those are the magic jewelry that Zo makes, the spells? that's Zo getting her shots in. The cool sword and close range fighting? that's Chell, using a cool magic weapon that Zo made for them.
While i did consider eldritch knight fighter subclass, fighter in 5e D&D is just kinda really loot dependent and i honestly am not here for that

In terms of communication, its a lot of Chell takes the lead and drives most of the body, with Zo picking opportune moments to flick out some magic, they at least practiced a lot of the basic things, and have a few callouts for more advanced concepts.

thats so good! I love a hexblade warlock
I originally conceived of my chimera ocs as a mage/fighter combo…

in the absence of a game setting, have you thought of just writing a story about them?

not at all lol
I figured they were a fun character design and something i wanted to try in D&D and i play by old D&D rules: The more backstory you write for your character the faster they die. Have two backups and never mourn their death.