This is the costume in which we see the main character at the beginning of the music video. The dark colours (mostly black) reinforce the problems he is facing, such as his violent nature. The colour red on the t-shirt can signify danger from his side, and helps the audience to identify him as the violent guy in the scene.
When going to his therapy session to get help, the character changes his appearance. He’s wearing less black, therefore creating the illusion of him coming to terms with his problem, and helping the audience identify that he wants to change. The grey colour also could signify balance, as it’s a cool, neutral, giving the audience and impression of a changed mindset.