WARNING: This post may contain spoilers from the manga. Please read at your own risk!
Prior to the events that have occurred in the anime, Levi originally lived as a thug in the underground city below the capital along with his friends, Isabel Magnolia and Farlan Church. They were later captured by Erwin Smith, who blackmailed Levi into joining the Survey Corps. Although Levi once wanted to kill Erwin, Levi later came to trust his commander, obeying his every command and judgment.
I’ve never seen cosplayers use this color for their Shingeki no Kyojin military uniform before! Not sure if this this official or not, but black looks really good on them, don’t you think? Thanks to Jane for sending this in!
Source: OH YE YA on World Cosplay