I am color, I am sound. I am all around. I help you gauge the mood. I am different shades of a hue. I define Music, art, literature, and even a fart. What am I

I travel without moving, yet show you the world.
 I open like a book but have no pages to turn. I have keys but no locks, a brain with no face. 
I sleep when closed, wake when you choose my place.
 What am I?

I change with minds and point of view, what’s true to me may not be to you.

What am I? I heal your pain, I was used before paper existed and I present you the world at your fingertips.

I am a group of cells with a similar function, like connecting, moving or protecting. In another context, you use me for wiping, cleaning or blowing.