Atmospheric Perspective
Atmospheric Perspective is the name given to the natural effect of distance on colours.
Here is an example from Three Sisters: Atmospheric Perspective in the Blue Mountains, a scene in the Blue Mountains, about 90 minutes drive west of Sydney.
Let's take a vertical section of this scene in order to more clearly see what nature does to colour.
Notice how the olive green becomes a blue green in the distance! Same trees, same day, different colour.