The name coolshades refers to a guy OVA2 who initially kept hidden from his commander Dog McCoy that Shun was working with the rebel forces. He also perceives Shun's feelings for Melinda.
In OVA3 a similar looking guy is seen talking to Alex Riger, indicating he may be a spy or double agent for the opposing parties.
hanging out with Erna.
Dog addresses him 25m50s into OVA3 as "Max" when he's suiting up to fight and Dog says he didn't ask mechanics to fight.