Gonna do a oc bio about the two, being demon hunters and protecting they're own city.

Red: one who is carefree and has a strong will to protect those dear.

Blue: one who is honorable and serious, has a strong will to protect others lawfully.

Difference between the two is the red one will kill the unpunished, while the blue one refuses to kill.

(References to yuri and Flynn from tales if vesperia)