Not so much of a story idea today, but more of a thought.
In children’s fantasy stories (movies mostly) it is rather easy to differentiate who is good and who is bad (excluding the traitors who are meant to fool you out) solely from each character’s demeanour and colour scheme. Generally, a lot of the members of the heroic side are knight-like and bathed in pure white, varying golden tones, or blues. The villainous personas seem to harbour more distant personalities and are assigned shades of black and/or red for some reason.
Therefore what if there was a story where the protagonist and the antagonist were presented in their respective colour schemes; with the story of course being told in the protagonist’s perspective so reality is slightly skewed to how the protagonist views events. From his role as a protagonist and his dashing appearance/colour palette, the audience may believe that what he’s doing is righteous and all for the sake of halting the villain’s ‘evil plans’.
However, by the end of the story, it is suddenly revealed that the seemingly heroic protagonist is actually quite villainous, and the antagonist, who is portrayed with what seems to be an extremely selfish and malicious personality, actually has the more righteous motives. They’re basically the opposite of what their design suggests. OR the story can be a slow descent where the truth concerning the natures of each character is revealed like a slow spreading poison and the fact gradually dawns onto the audience’s increasingly dread-filled minds.