I can't draw, but I would imagine Blu as some scowling tough biker dude with thick eyebrows, spiky hair and a general 'angry' feel about him.
Charry would be a hilarious chibi with red hair as the exact opposite of Blu: friendly, happy, and with a shirt that says ‘Feed!’. Strange ideas, but I kind of like them.
These aren’t based on looks, but rather on personality. Blu is a grump whose motto is “If it moves, flare!” Charry is a friendly guy who swims up to the front of his tank whenever I walk in, just begging to be fed.