Answer:
When it comes to me you go on red and stop on green.
You can catch me but cannot throw me.
If you lose me you may cause people around you to lose me too.
The warmer I am, the fresher I am. What am I?
I tremble at each breath of air, and yet can heaviest burdens bear. What am I?
I build up castles. I tear down mountains. I make some men blind. I help others to see.