Why Does Yellow Turn Green When You Add Black?
As I stated in the introduction, the dull green is the actual color of dark yellow. If you don’t think this is correct, then what color should dark yellow be?
Below is a screenshot of the sRGB color space that’s in use by digital cameras and computers. I used the ColorSync Utility to view the range of colors that are available in this color model. If you have a Mac, you can find this application in the Utilities folder. The ColorSync Utility creates a 3D model of the entire range of colors that you can capture within this color mode. You can rotate it in any direction to view all of the colors, and inspect if from any angle. I rotated it so the mixture of red and green is visible.
In the RGB color space, yellow is a secondary color that’s the result of mixing red with green. This may be confusing because mixing color with light is different than mixing paint. Graphic artists who work in the RGB color space are more familiar with mixing yellow.
Anyway, the important observation here is that pure yellow takes up a very small portion of the where the red and green overlap near full intensity. Only the top part of the graphic below is pure yellow. If you follow the yellow downwards towards black, it immediately begins to turn green as it becomes darker.
Below is the same graphic but I sampled the green sections directly below the pure yellow. The colors become darker towards the bottom of the color model. I created swatches of the colors directly below the pure yellow and placed them to the right. Viewing them on a gray background will make it easier to see how it turns green as it gets darker.
When you try to darken yellow with black, it turns green. One natural inclination as a painter is to try and neutralize the green with red. But that just makes it turn brownish orange. You can see the same effect in the sRGB color model. If you sample the colors to the left of the darker yellow greens, they’re more of an brownish orange as shown in the swatch in the graphic above .
Color Is Subjective
Your perception of color is subjective. This is because the surroundings have an influence on way a color appears to your eye. For example, if you place red next to green it makes both colors appear more vibrant.
Above is a graphic that contains two gradients. The top one is pure yellow that transitions to black. The gradient below it is a pure green gradient that transitions to black. The vibrant green makes the dark yellow appear less green. Colors are influenced by the other colors nearby.
The way the pure white of a canvas can make it difficult to judge the values of your colors is another example of how surrounding colors can influence your perception of color. The white of the canvas is so bright, it can make the colors on the canvas appear darker than they are. This is why some artists tone the canvas with gray or a neutral earth color before they begin to paint.
One thing I noticed is the dull green shadow doesn’t look very green when it’s surrounded by a field of yellow, or placed in the context of a yellow object. It’s when you isolate the shadow color that it looks more like green. Most people probably wouldn’t notice that the area where the two shapes intersect in the graphic below is green.
Conclusion: Dark Yellow Is Dull Green
Yellow turns green when you mix it with black. The above experiments involve the way light behaves and have nothing to do with artists paints. When you see a yellow object in shadow, it’s the same shade of dull green that these experiments produce. There’s no such thing as dark yellow that’s not a dull yellow green. There’s no other option.
What’s important to understand as a painter is that yellow and black creates dull green so that you can take advantage of it. For example, some artists use the Zorn Palette which doesn’t include blue or green. They mix green by mixing yellow and black.
Another reason why you should know this is so that your color mixing is predictable. You’re not confused when yellow turns green as you mix it with black.
You can read about how the cones and the rods in your eyes work, but that usually doesn’t lead to any improvement in your painting. What does create progress in your work is to mix color, make observations, and learn from it. Become familiar with the colors that you have on your palette and the mixtures you can make from them.
Keep in mind that color mixing isn’t new, you can build upon the results of other artists. You don’t have to figure these things out through trial and error. Click on the “Color” category to view all of my posts about mixing colors. You can also download my free acrylic color mixing chart and use it as a reference when you paint.
