The Law Book
Darkness and Light will be born into a world where supernatural laws to not exist. Their genders mean nothing, their true forms will appear in time. Their powers will break free.
Darkness is born to be shunned. Darkness is expected. Darkness is something there, that you can never escape.
Light it born to be excepted. Light is needed, not unnessasary. Light is something there, that you never want to escape.
Light will be loved, Darkness will be hated. Due to these circumstances, they are incompatable. Black and White make grey which does not exist and if it does, they worlds balance will collapse. A child born of Darkness cannot converse with a child born of Light.
The last pair to exist will accept eachother. They will create Grey and distroy the world they hold so dear to them. Centuries of being kept apart will melt away and Grey will cover the land, destroying all in it's path.
Grey cannot exist. Colours exist to prevent this from happening. The Colours will protect the harmony of balance.