Answer:
What is at the end of a rainbow?
I'm really blue but when you see me I'm red. You don't see me too often. I'm there for you if you're hurt.
I am a cave full of bones and the house of a worm.
I am the only word that looks the same when spelled upside down.
Kings and queens may cling to power and the jester's got his call. But as you may discover the common one outranks them all. What am I?
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.