You're talking about passing gas flatulence
A time when they are green, a time when they’re brown, but both of these times, cause me to frown. But just in between, for a very short while, They’re perfect and yellow and cause me to smile!
What am I talking about here?
I am a being with many faces. My first is peaceful and calm, but can kill you. My second is strong enough to smash ships but still fears the sun. My third flies when it's born and runs when it's dead. My fourth goes away and never returns. What am I?