Dawns Away The Day's Turned Grey Riddle

Answer: The Sun or a shadow. The riddle is written as if the sun is speaking to us. It's not saying the sun tracks its light; it's saying:

• “I’ll be back” → the sun will rise again.
• “And then we’ll track the light”→ we(humans) will follow, notice, and live by its light through another day.

  the sun leaves (sets), returns (rises), and then together with us it “tracks” the day—meaning we move through the day guided by its light. If you don’t like that reading, a more literal alternative answer that fits the “tracking light” idea nicely is a shadow   Source: https://www.riddles.com/1392