I suspect this is wrong -- some things don't match up perfectly -- but some parts may be right, and it may inspire a better answer from someone else. Perhaps this is a description of
a fox hunt. [EDITED to add: OP has indicated in comments that s/he was thinking of a different animal being hunted: a wild boar. Most of this could also apply reasonably well to hunting deer, but in what follows I'll stick with foxes and boars.]
At the beginning, It came from the dark green.
Foxes (in the wild) live in forests. [So do boars.]
At the end, It returned to the deep brown.
Most animals, when dead, end up in the earth. [Boars as well as foxes.]
It loved the deep brown even before It left the dark green.
But not for the same reasons.
Foxes dig burrows under the earth. [Boars don't dig burrows but do get very muddy.]
He took It for them, from the dark green.
He is a human hunter and they are the other humans in the hunt. [Boars, unlike foxes, are hunted for food -- so in this case "they" are the hunter's family or customers.]
The foe who took It, had an accomplice.
I think the accomplice is a foxhound, suggesting that "he" above is human rather than hound. [Or, of course, a boarhound.]
The accomplice wasn't a foe, but was serving one.
Dogs aren't particularly the enemies of foxes, usually.
It shouldn't have trusted Her.
She is the accomplice, the hound. (For reasons I am not unsure of, it didn't occur to me before reading OP's comments that this was a possible assignment. I think I'd initially taken "he" to refer to the hound a few lines earlier, and was confused by that.)
Pride is mine, he said!
Thank you, they said.
Hunters are often proud of their hunting accomplishments. [If "they" are getting nice tasty boar meat, they should indeed be thanking the hunter.]
Loyalty, she would say.
Of the foxhound to its owners. [Or the boarhound.]
Crime, Slaughter, Slavery... It would say.
And say many more cruel things.
If It could.
The fox would disagree. Except that of course foxes can't really talk. [Neither can boars.]