Let us take 2 movies and 1 scene from Breaking Bad to demonstrate how simple things like dress colour can be used to indicate character transformation.
This you might have observed yourself. On the initial stages of the movie, Vikram the cop believed that there is only the good(white) and the bad (black) and no in-between. Remember the first interrogation between Vikram and Vedha? Vikram was seen sporting a white shirt, meaning he was a good man. Over the course of the movie, Vedha makes Vikram realise the mistakes Vikram unknowingly/ ignorantly committed. Now let’s jump to the final scene, what was Vikram wearing? A grey shirt (combination of black and white). Meaning, he is neither a good guy nor a bad guy. This is a very subtle way of indicting that a character has undergone a transformation.
This Mani Ratnam masterpiece make use of colors like no other Tamil movie. The three leading men are represented by three colours: Madhavan : Red, Surya : Green, Siddarth : Blue.
Let us take Siddarth’s case. Blue is a pleasant color by nature. Blue represents joy, bliss and happiness. Siddarth when introduced was a happy go-lucky boy-next-door. But after meeting Surya(who predominantly dons green), he aspires to become like Surya.
Now jump to the final scenes of the movie. Siddarth contests in elections like Surya, wins it like Surya. How does Mani Ratnam show us that Siddarth had become like Surya? Does he add voice overs or monologues indicating the changes Siddarth underwent? No, Siddarth now wears Green- The color represented by Surya throughout the movie. This is one kick-ass way to indicate character development/transformation.
Some characters stay with you for your lifetime. One such character is Walter White. If you have seen BB, there is one scene which always comes across our mind. Yes, I am writing about the epic “I am the one who knocks” scene. Walter, before arguing with his wife Skyler, was wearing a red shirt. As Skyler confronts Walter, he gets agitated. Walter before delivering those famous lines, starts to remove his red shirt revealing another t shirt in darker red inside his shirt. Meaning, he has become an evil guy not only from the outside, but also from the inside. Now imagine the same scene with Walter wearing a simple light blue shirt throughout the scene. The impact would have reduced hundredfold.
If you are writing a script, don’t just think about the plot and characters. Think about their outfits too. If they are undergoing a character transformation, find ways to indicate them subtly. I’m not saying that this is the only way. There are other ways too… like in Baby Driver, it’s not dress. It’s the sunglasses! Next time when you watch the film, notice how Edgar Wright gradually makes our protagonist’s glasses disappear. Initially, Baby was a negative character and wore glasses. Towards the end, Baby starts transforming into a positive character and note how Baby has a half broken glass as he is on his way to becoming a good man, to Baby not wearing glasses as he has become a good man.