Mix blue and yellow
Mixing green color seems to cause problems for many. Maybe it’s because mixing color is generally difficult or it’s just that green colors are difficult to get right.
When a blue color is mixed with a yellow, the result is a green color. But there is quite a difference between the different greens that can be mixed with different pigments. The purest color mix occurs when you mix a pure and cold (greenish) blue with a cold yellow because they are quite close to each other in the color wheel, but if you mix a reddish blue with a yellow-orange, the result will be much less clear.
As cold blue colors, I usually classify Phthalo blue (both red shade and green shade), Prussian blue and cobalt blue. Cobalt blue is actually warmer than primary blue but so cold that it may fall into this category. There are also cerulean blue, manganese blue and cobalt turquoise, but they are so light and milky cloudy that they work doubtfully in green color mixtures. Cobalt blue gives a mild green color mixture together with a yellow color, because it is a bit whitish cloudy. Cold intense blue colors like Phthalo blue or Prussian blue give nice clear green mixtures along with almost any yellow.
Warm blue is French ultramarine and indantron blue. The less common cobalt blue deep also falls into this category. Green color mixtures with the warm blues and a yellow color give less pure results than with the cold blues. The mixtures with warm blue often become beautiful green colors, which can be made deep and intense but which are not really right for spring green birch.
Therefore, choose cool intense blue colors such as phthalo or Prussian blue for clear pure green mixtures. Choose cobalt for milder lighter greens while the warm indatron blue and French ultramarine go well with dark intense greens such as spruce and pine forests and the like. As for yellow colors, a lemon yellow gives clearer color mixtures than a warmer one. If you want to achieve a clear light green color, choose phthalo blue and lemon, for murky dark greens, choose ultramarine and some warmer yellow instead.
To control the degree of purity of the mixture, artists like to use red. The red color should be cold, e.g. quinacridone rose or alizarin. This is also done to create dark green colors, more info about red color in green color mixtures will come later.