Answer:
I spend most of my day eating white. When I am quick enough I get rewarded with fruit and something blue. In a dark room with blue walls I run from the ghosts that roam the halls
I am round as an apple, deep as a cup. All the King's horses can't pull me up. What am I?
I am owned by every man though my length differs. Their wives uses me after getting married.
I'm as simple as a circle worthless as a leader; but when I follow a group their strength increases tenfold. By myself I'm practically nothing.
Whoever makes it, tells it not. Whoever takes it, knows it not. Whoever knows it, wants it not. What am I?
What is lighter than what it is made of?