In the scene we can see that most of the guests in the shot are wearing very similar outfits. The Joker truly standout in this scene with his purple jacket and green waist coat because of how contrasting the outfits our. This shows the audience how important the Joker feels about himself. He feels the need to standout. Another reason for his contrasting look is because it represents what that Joker wants disorder.
Another thing to focus is how the camera is used with the Joker. When Joker is giving his monologue the camera shakes a bit and goes around with him moment. This makes the audience feel as if they are in the scene with him. The rushed movement also shows us how the Jokers thought are running through his mind. A clear moment is when he attacks Rachel and the camera spins around his head.
One more thing to note is the props, in particular the Jokers knife (more like a shiv). Although it does look threatening he doesn’t use it. It seems more like an add on to his hand more than anything. Yes, he does use it to threaten Rachel as its right in her face it’s his own hands that hurt her when he’s harshly grabbing on to her face. The shiv is symbolism for the jokers craziness and his sketchy life.