Simplify your palette by mixing your greens
A lot of artists have trouble with green because there are so many shades to mix and so many types to buy. What I've come to understand about green is that less is more. Simplify.
Removing most of the greens off of my palette made a positive difference to my paintings. If you want harmonious greens you have to mix them. I now carry only one green, Viridian, a green with subtle blue undertones that also makes nice turquoise colours.
Most of my greens are a mixture of Ultramarine Blue and Cadmium Yellow. This combination covers about 75% of the essential greens. When I need more vibrancy, I use Cadmium Yellow Light instead of Medium. And if a nuclear green is needed, I switch to Manganese Blue, which already carries a high green content.Unless I'm painting very vibrant colours I almost always temper my greens with a dash of red. The addition of red seems to deChernobylfy the usually scorching power of green. A tiny (and I mean tiny) bit of Quinacridone Red makes the green sit down and pay attention.
An important point to remember when painting with green, especially on trees, is to keep transparency in the shadows. Transparent darks in a tree recede up into the mass of the tree and give the appearance of depth. Ultramarine Blue is very transparent and will carry the small amount of opaque Cad Yellow needed to mix a green. This allows for the top leaves that catch the light to look as though they are popping out over the shadows.
Note: Keep bushes, shrubs and trees in check by making sure they get lighter near the tops. The more horizontal something is, the lighter it becomes. So, as the bottom foliage starts to rise and curve towards the top of the tree it should become lighter.
Another problem area for artists seems to be the lack of temperature change within greens. To make greens more alive, think in terms of warm and cool. To cool a green one can swing it over to the lemon side of yellow or add a smidgen of Manganese Blue in with the Ultramarine Blue + Cad Yellow mix. Don't forget you have Viridian at your disposal for cool greens. Viridian and Quinacridone Red make a great sage colour.
If you want a warmer green try using Yellow Ochre - you can now add a touch of Cadmium Orange to further warm your green. One thing I have found is that most brands of yellow contain a fair amount of green content in them, making for easy mixing of greens. But this can have drawbacks, especially if you want to paint fall scenes. After many failed attempts at fall trees I found the problem lies in the yellow. If you want convincing fall colours switch your Cad Yellow Medium to Deep, which has no green content and has more orange in it, making for smoother transition into the warms.
With the elimination of greens from my palette I have found it easier to control my palette. My greens are fresher and I can put away the bullwhip as they now seem to respond to my every command.
You have been given the green light to go and paint a painting that will make everyone green with envy.