The core mechanics are simple: you change colors depending on how much you let others influence you. as you change, so does the world around you, making your progress ever so grey and dull.
The people you encounter aren’t enemies, they just think differently than you do.
That means that if you want to change their mind and make them brighter and more colorful you will need to learn to talk to them.
They will try to make your life and everything around you sad but that only makes your path all the more rewarding!