Thank you for the kind words about the music and atmosphere!
To answer your question: The colors represent the boy's internal state. Green represents the 'sweet spot' of courage, while Red means the tension is off-balance (over-thinking).
You see the future images in both versions because he is always imagining it, but the ending changes depending on your input. If you can keep the shadow Green for enough time, you will unlock the another ending. I hope you give it another try! Thanks again for trying my work!