(Before I start, I need to mention that this is the first color duels I've seen) So I need help for changing my profile to the team I'm on. I don't see an option to change the profile pic to have a green or purple tint.How do I change it?

The profile tint appears by itself on the Color Wars board only. You cannot pick your team, it's determined at birth calculated based off your user ID.

If you can see this thread you are on the Green Team -- if you can't see it, you're on the Purple Team.