You may find it perplexing that yellow turns green when you mix it with black. Some artists use this to their advantage when painting with a limited palette, but it can catch you by surprise if you aren’t expecting it.

So, why does yellow turn green when you add black to it? Dull olive green is an accurate representation of dark yellow.  Some of the yellow and black pigments will produce an exaggerated green because of the blue bias of the pigments. However, you can observe dull greens in the shadow shapes of yellow objects because that’s the color of dark yellow.

Three Experiments That Show That Dark Yellow Is Dull Green

Below are 3 experiments that you can conduct that proves that dull green is the color of dark yellow and that it has nothing to do with the black paint. Some artists suggest that black pigment contains blue that makes the yellow turn green. This hypothesis is easy to test. I should point out that some black pigments are biased towards blue, but yellow still turns green when you mix it with a neutral black. The green mixture at the top of this post is Cadmium Yellow Light and Mars Black. This is an example where the pigments create an exaggerated green.

1 Cast a Shadow on a Swatch of Yellow

The wood block casts a shadow onto the yellow rectangle. Notice the shadow is the same dull yellow green as the bottom swatch in the color book.

The simplest experiment is to paint a sheet of paper yellow and cast a shadow on it. Yellow is difficult to photograph, but you will get the idea by viewing it with your eyes. You may need to view the shadow through a hole in a white sheet of paper to see the color accurately. If you’re interested, try mixing the color that you see and compare it to the shadow.

In the photograph above, a wood block is casting a shadow on a rectangle of pure yellow. When you look at the shadow it may not appear green to you. But if you isolate it from the rest of the scene it’s the same dull green you get when you mix yellow and black paint.

On the right side of the photograph is a Pantone color book. These color books are used in graphic arts, interior design, and printing. I used the book to quickly find a color match for it, which is faster than painting it by hand. The closest color swatch is Pantone 105, which is Process Yellow with Pantone Black added to it. The recipe is visible in the photograph right beneath the color swatch.

The color of the shadow is created by casting a shadow across it to make it darker. No pigments are involved in creating the dull green. The dull green shadow is the result of lowering the intensity of the light that reaches the yellow rectangle on the paper. There’s no black or blue pigments involved, that’s the actual color of dark yellow.

2 Visual Blending

It’s possible to blend colors without physically mixing them. “Visual color mixing” is a concept that the impressionists took advantage of. The idea is if you create a pattern of small dabs of color next to each other, they will start to blend “in your eye” when you view them from a distance.

Visual blending also happens in commercial printing, where a pattern of tiny halftone dots creates a full range of colors. All of the colors that you see in magazines are created with only 4 colors printed in a pattern of dots.

I can eliminate the idea that it’s some impurity in the paint that’s causes this by placing small black dots on a yellow background, similar to halftone dots. Of course you have to stand at a distance from the painting for the colors to blend. Otherwise, all that you’ll see is a pattern of black dots on a yellow background.

Painting small black dots with a small paintbrush is tedious, but it’s a simple task for a computer. An inkjet printer can quickly place colors in a very accurate manner. It also eliminates the possibility of the colors overlapping or blending with each other on the paper. Below is a close up of the black circles on a pure yellow background that I created in Adobe Illustrator.

This is a pattern of black dots on a yellow background. When you view it from a distance, the two colors will blend in your eye. The blending doesn’t involve the physical blending of black and yellow pigments.

I printed it out and took a picture of it from a distance. As you can see in the photograph below, when you view it from a distance it creates a dull green. The graphic is hanging on a wall at a distance, while the color swatch is closer to the camera. The yellow green on the left side is the printed pattern of dots, and the right side is Pantone 397 which is a yellow green.

The dull green on the left is the result of viewing the pattern of yellow and black dots from a distance. The yellow and black dot pattern is in the circular inset. The color that it creates is very similar to the yellow green color swatch at the top right, Pantone 397.

I was able to blur out the pattern of dots by focusing on the color swatch which is closer to the camera. If you look at the close up of the printout on the left, it’s a pattern of pure yellow circles on a black background–it doesn’t contain green at all.

3 Create a Yellow and Black Gradient in Photoshop

Another experiment that you can easily replicate is to open up a graphic arts application, such as Photoshop, and create a gradient from yellow and black. The middle of the gradient contains a variety of dull greens. The green becomes much more obvious if you separate a small section of it and surround it with white.

This is a Photoshop gradient that spans from yellow to black. The green swatch at the bottom is the color that it creates in the center of the gradient. Photoshop reflects the way light behaves and has nothing to do with pigments, the green is created with light on a computer screen.

Since the color mixing takes place on a computer, it eliminates the variable of using black pigment. The computer creates colors through mixing light. Yellow is created by mixing equal proportions of red and green so there’s no blue included in any part of the gradient. Below are the RGB values for the different parts of the gradient.

  • Pure Yellow: R255 G255 B0
  • Yellow Green in Middle: R128 G128 B0
  • Black: R0 G0 B0

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