Common Sense Evaluation

When you see pink, sky blue, orange, or red
It would be wise to turn my yellow head

In a dark room with blue walls
I run from the ghosts that roam the halls

What am I?
 

Tomorrow you’ll have more;

As your time passes,

I’m not easy to store;

I don’t take up space,

But I’m only in one place;

I am what you saw,

But not what you see.

What am I?