the important thing is the value.
"keying off the sky" and "keying everything below the sky"—squinting the eyes to compare the light to the dark, and to the sky to find the value relationships.
These are the base-greens, and they can be adjusted with the complimentary reds or oranges to make them grayer. Depending on the sunlight; if it’s an evening light, then you add more red or orange.
- Ultramarine Blue & Yellow Cadmium mix a “vibrant dark green”; adding a bit more ultramarine blue, a bit less of the cadmium yellow, and a touch of cadmium red will make this mixture a darkest possible green.
- Ultramarine Blue & Yellow Ochre mix a chalky and grey mix. This mix is not often used as a green. If it’s used, it’s occasionally used in tiny bits for “olive tree greens”, but to get the olive green you have to add a bit of cerulean blue and a bit of white to the mix; and you can knock it down with a bit of the vermillion.
- Cerulean Blue & Yellow Ochre is a good dark green mix for any distant large trees. if you add a bit more yellow ochre to this mix, “it’s a perfect color for cypress tree in sunlight”.
- Cerulean Blue & Cadmium Yellow is a base mix for “grass green” or “fig tree in sunlight green”. if you want to get the grass color, you add more cadmium yellow and more white.