Weird. It should've completed as part of the same event that gave you the next quest. Sorry for the trouble.
Thankfully no, it'll only be a visual bug.
I'm not sure how it happened, since The Color Green should only be active if you never started Green With Rage (the aggressive path). The only time it wouldn't be active but still in your quest log is if you failed the first step and were forced to switch paths, but then it'd be failed, not active. I'll have to dig into that more to try to figure out what happened.