Evolution is throwing things against the wall and seeing what sticks (by sticking I mean reproducing bc you have better traits). If every single one of their prey and predators have this color blindness then orange and green would have the same effectiveness and whichever trait comes out first. If a prey/predator evolved to have better color vision then it would quickly become a disadvantage and after millions of years it's possible they evolve to have green fur.

There could be other benefits like being easier to attract mates.

Also some animals can see infrared, so even if their fur was perfect for the environment they could still have issues by being spotted, in which case the color doesn't matter as much and the colors for mating becomes more important.

Edit: Wording.