Paper makers are racists.
No, for real. Paper is white because graphite is black and you can't write on black paper with black pencil, can you? Well, you can but you won't be able to see what you write. Anyway, when you cut paper so thin from the trees you get white. It's like...the tree is so condensed and when you begin to cut away little pieces it changes from dark to light. I don't know. I'm just ramling with my theories at 4 in the morning...