James Potter was black and white. From his tousled black hair, to his crooked white smile. For him there was good and bad, bravery and cowardice, right and wrong. He liked logic. He liked rules, even if he did enjoy breaking them. He liked clear cut boundaries and simple answers.
Lily Evans was colorful. From her vivid red hair to her bright green eyes, there was nothing black and white about her. She was a mixture of two worlds, muggle and wizard, and some days it was hard for her to decide which one she fit in better. For her nothing was black and white. Everything was somewhere in between. There were good friends who made poor decisions, and mean boys with good morals, and lovely quiet friends with hidden inner monsters and pretty sisters with ugly temper colored her face and her tongue colored her mouth.
James gave Lily lines to color within. He helped her to distinguish the difference between toxic friends whose beliefs diminished the validity of her very life, and arrogant school boys whose hearts were in the right place but whose heads were six feet up their ass. He helped her to see that even though the world isn't black and white, sometimes you still have to pick a side. And most importantly, he showed her that true, blinding goodness and bravery still existed.
Lily added dimensions and hues to James's world which he didn't even know existed. She showed him that not all good people are faultless, and not all bad people are fundamentally evil. She taught him that no question worth asking ever has a simple answer. Perhaps most of all, Lily Evans taught James Potter that some things, like real deep-rooted evil, and boundless love, and lifelong friendship, defy logic and reasoning, and are all the more powerful for it.