This is "Something Green" by Fredric Brown (1951)1. It is about an astronaut named McGarry who crashes on a planet with only red vegetation and has a "little five-limbed creature" named Dorothy who he talks to about wanting to see green (emphasis mine):
He stopped ten paces short of the edge of the red jungle and aimed the sol-gun at the bushes behind which the lion crouched. He pulled the trigger and there was a bright green flash, brief but beautiful -- oh, so beautiful -- and the bushes weren't there any more, and neither was the lion.
McGary chuckled softly. “Did you see that, Dorothy? That was green, the one color you don't have on this bloody red planet of yours. The most beautiful color in the universe, Dorothy. Green! And I know where there's a world that's mostly green, and we're going to get there, you and I. Sure we are. It's the world I came from, and it's the most beautiful place there is, Dorothy. You'll love it.”
Another astronaut shows up and tells him Earth was destroyed, then McGarry shoots him:
“Earth is -- gone? I don't --”
“Not gone, McGarry. It's there. But it's black and barren, a charred ball. The war with the Arcturians, twenty years ago. They struck first, and got Earth. We got them, we won, we exterminated them, but Earth was gone before we started. I'm sorry, but you'll have to settle for somewhere else..."
McGarry's sol-gun came out of its holster. McGarry shot him, and Lieutenant Archer wasn't there anymore.
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1 from Wikipedia