Answer:
I am pronounced as one letter written with three. I come in blue black brown or grey. Reverse me and I read the same either way.
In a tunnel of darkness lies a beast or iron. It can only attack when pulled back. What is it?
I can be simple or I can be complex. I can be found in this riddle or in everyday life. I can be shapes or even colors.
I have a name that's not mine and no one cares about me in their prime. People cry at my sight and lie by me all day and night.
I go up when the rain comes down
What is always coming but never arrives?