Never forget that you can tweak a green by adding blue to it. Again, different blue pigments will result in different greens. If you're painting a landscape, start by mixing in a little of the blue you've used for the sky rather than another blue. Not only will it give you a slightly different green to use, but it'll help the composition by creating a subtle color link between the greens and sky.
Landscape greens appear more blue or yellow depending on the time of day, and the angle of the sunlight. Adjust your greens accordingly. The most extreme is the short window of golden light near sunset that photographers love so much, where the sun throws a golden glow over a landscape.
