Only one color, but not one size, Stuck at the bottom, yet easily flies.
Present in sun, but not in rain,
Doing no harm, and feeling no pain.
What is it?
Let's see who's the smartest :) ❕❕❕❕

your answer is SHADOW

A shadow

Explanation:

It is stuck at the bottom because if it always below you, but it flies because it travels at the same speed as light, the sun is what creates it, and you need the sun to have one.

coal is not sustainable because it will one day run out.