Among us may be a social deduction game, but it does, to a certain extent, rely on the players' pre-conceived notions about colors. Assumptions of who the impostor might be are done even before the game begins, and these are made based upon the colors that the players see around them.
Why is red 'sus' in Among Us?
You could blame game marketing for that reason. People have always used red to be a color that signifies danger. The flashy red signs that occur when there's a sabotage, or when dead bodies are reported, always reinforce the fact that red is indeed dangerous.
It's more of a psychological thing. The way the color red is portrayed makes people wary of the red player. Even if you have a look at the poster of the Among Us, the red player is right at the center and draws all the attention. Smart impostors tend to use this factor to their advantage, using the red crewmate as a decoy to hide their intentions in game.
Another reason red draws all the attention is because of the way the color has been used in every other game. Take GTA for example, where your minimap flashes red when being chased by cops, or even Destiny 2 , where your health bar flashes red when your health is almost depleted. The usage of red to describe danger, is the reason why the red crewmate attracts so much heat from the other players.
If we are to look at it from the colored perspective, Among Us takes on an entirely different psychological angle. A pink crewmate won't be as suspicious as a black crewmate or a brown one. That's because we've always associated the color pink with things that are cute and fluffy.
While players subconsciously use color theory to predict who the impostors are in Among Us, the reality is that any player portraying any color could be the killer. So don't let those colors fool you. Trust no one but yourself.