Justin Bieber Purple Reign

1/17/2016 6:58 AM PST BY TMZ STAFF

0117-justin-bieber-instagramJustin Bieber wanted to show the world his purple hair is boss, and the rest of his body went along for the ride.

Justin posted the pic Saturday with caption, "Back at the gym."  Translation ... he's not ready to throw in the towel. 

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