I heard of an invading, vanquishing army sweeping across the land, liquid-quick; conquering everything, quelling resistance. With it came darkness, dimming the light. Humans hid in their houses, while outside spears pierced, shattering stones walls. Uncountable soldiers smashed into the ground, but each elicited life as he died. When the army had vanished, advancing northward, the land was gree and growing, refresh.
I am pronounced as a one letter alphabet.
I am written with three letters.
I am complete with just two letters.
I am double.
I am blue I am black I am brown I am gray I am yellow and I am green.
I can read from both ends.
I appear the same every way!
What am I?