Abnegation

"The Abnegation faction values selflessness. They believe that if you protect yourself from vanity, greed or envy then you will see everyone as being equal and won't envy others. Those in Abnegation are often reserved and don't draw too much attention to themselves."

Those in Abnegation wear very plain, gray clothing. They try to hide their beauty so they only have plain hair styles and they don't wear any accessories, except for a watch."

- https://www.ksat.com/news/2014/03/14/divergent-inside-the-factions/