Mixing Color–A Short Physics Lesson

I accidentally discovered Blue and Yellow Don’t Make Green, by Michael Wilcox. I ordered the book on a whim, and it has now become one of the most important resources among all the books I own on the subject of art.

I decided to tell you about it, just in case your experience with mixing colors has been as disappointing as mine.

If you’re a professional artist who figured out color mixing years ago, this post won’t mean much to you. However, I struggled for years trying to understand why the colors I mixed for my paintings and craft projects never came out right. I was obviously doing something wrong. After reading this easy-to-understand book, I now realize that I didn’t understood the basic physics of color.

This was particularly upsetting to me because the animals I like to paint are often clothed in subtle, interesting shades that I couldn’t match on my palette.

After reading Wilcox’s book, I realized that I learned to mix colors the wrong way back in grade school. That’s when I learned that yellow and blue paint make green paint. Red and yellow make orange. Red and blue make violet.

It sounded so simple. So why couldn’t I mix these colors and make the hues I needed?

Since I didn’t understand the underlying physics of color, (and neither did my grade school teachers), most of the colors I tried to mix on my palette turned into mud.

If you mix blue and yellow paint you will get green–or something close to green. But it never seems to be the green you want. It’s very often a muddy, grayish stuff with a greenish cast–or it’s a brash, neon color that isn’t at all what your painting calls for.

Yellow and red do make orange, but what if you really wanted a muted, almost brown orange–or that specific hue that you see in a particular animal’s eyes or frog’s skin pattern? Just start adding this and that–and end up with a muddy color that’s almost, but not quite, the color you wanted.

Blue and red do make violet–or a grayish mud with a violet overtone, depending on which blue and red you mix together.

When you do manage to mix a color that’s perfect, will you be able to reproduce it next week? Only if you take very good notes, and frankly, I don’t know anyone who does. But maybe your memory is a lot better than mine.

Of course, if you’ve taken a university-level course in color mixing, you’ll think this whole post is silly. Your paintings and craft projects will be filled with exactly the right colors, both bold and subtle, and those colors make your creative spirit soar.

But you only have to stand in front of the display of artist’s paints at the art store, or the acrylic craft paints displayed at your local WalMart, to see that I’m not the only one who can’t figure out how to mix colors. Manufacturers make hundreds of different hues, just for us poor folks who can’t quite figure it out.

Even the vast array of pre-mixed colors available at the store won’t help you get those muted grays that are so important in many paintings.

So, if you’re anything like me, you seem to have several options:

1. Never start a painting or craft project that doesn’t use pre-mixed colors available at the local store; or,
2. Find a book that shows swatches of thousands of colors, along with the formula for each, and thumb through it endlessly to find the color you need; or,
3. Start an ambitious project that requires subtle, interesting colors and then try to mix them on your palette by adding a bit of this, a bit of that–and then decide the muddy color you end up with is “close enough;” or,
4. Just give up and announce that you can’t paint.

I’ve tried all these options, and none of them has been been very satisfying.

That’s why I’m so excited about the book Blue and Yellow Don’t Make Green. Mr. Wilcox explains exactly why my previous attempts to mix colors was so often unsuccessful (his explanation goes against everything you learned about color in school), and then he shows how to mix exactly which colors you need–including those elusive grays–every single time, using a very small number of pigments. It’s not only easier to get the colors you want, but it’s also less expensive than buying a new hue every time you run into a difficult color.

Let’s talk about green, since it’s mentioned in the title of the book:

When blue and yellow light lands together on a white surface, green light bounces back. So it really is true, when speaking strictly of colored light, that blue and yellow make green.

However, a painting (or the surface of a painted craft project or paper mache sculpture) is not made up of light. It’s made from colored pigments that absorb or reflect light, which is an entirely different thing.

And that’s why trying to mix paint as though it were pure light simply doesn’t work. Your grade-school teacher may have insisted that it would work, but it won’t.

Mr. Wilcox explains this problem with a short physics lesson, which I’ll try to recreate here.

When white light hits a surface that has been painted blue, every color except blue is absorbed into the surface, and blue light is reflected back to your eyes. You knew this already, of course.

When white light hits a yellow surface, the same thing happens–except this time every color except yellow is absorbed, and yellow is reflected back to our eyes.

Mix all the colors on your palette together to make black, and the paint will absorb every color of light, so no light at all is reflected back to our eyes.

If colored paints were actually pure color (which they are not), every time you mix any two “pure” colors of paint together you would get black. The bits of blue in the blue paint would absorb the red and yellow light, and the bits of yellow paint would absorb the red and blue light. No light would escape from the paint, and you’d see a perfectly black surface.

This doesn’t really happen because paints aren’t pure. Some light does escape when we mix two colored paints together. The problem is, the color that escapes is often not really the color we wanted or expected.

So, let’s mix two colors that really do make green:

A greenish blue, like Cerulean blue, reflects mostly blue and a little bit of green.

A greenish yellow, like lemon yellow, reflects mostly yellow and a little bit of green.

Mix them together, and the blue and yellow (plus any red, purple, and orange) will be absorbed, just as one would expect. However, since both colors also a bit of green, the green from both pigments is able to escape from the paint surface and is reflected back into our eyes. You have just created green paint.

It isn’t the blue and yellow mixed together that made green–in fact, the blue and yellow cancel each other out. However, we do see green because green was reflected by both pigments.

This seems so obvious to me now, but until I read the explanation I just didn’t get it.

So what happens if we mix together a blue and yellow that reflect only a very tiny amount of green?

When you mix a violet blue, like Ultramarine, with a orangey yellow, like Cadmium Yellow Light, you end up with grey. There will be a greenish cast to your grey, and it may be exactly the grey your painting needs. However, if you didn’t want a muted gray with green overtones, you’ll end up adding a bit of this color and that color in order to “fix” it, and end up with mud.

Since no paint color is pure blue or yellow or red, every paint color will reflect a tiny amount of the other colors in the spectrum. Even Ultramarine blue and Cadmium Yellow will reflect a little bit of green. That’s why the grey or brown you end up with when they’re mixed will be a very muted green. There are times when that’s exactly what your painting needs.

One of the reasons that I’m so excited about this book is that it opens up many more species for me to sculpt with my paper mache clay. In the past I tended to avoid any critter that has a fur or skin pattern that I knew I wouldn’t be able to paint correctly. Now that I understand the basic physics behind colors, (and with the help of the color swatches in Wilcox’s book) I’m confident that I can move forward with my chosen medium.

Do you know of another book that helped you understand how to mix or use color in your crafts or paintings? If so, I’d love to hear about in the comments below.