Answer:
I help engines spin and pants stay up
By Moon or by Sun, I shall be found. Yet, if there's no light around, I am undone. What am I?
First I may be your servant's name; then your desires I may proclaim; And when your mortal life is over hold all your wealth within my power.
I have every color but no gold.
The more of me there is the less you see.
It's what light turns into in the night