What makes a color cool vs. warm?

We’re often taught that cool colors are blue, green, and purple.

Whereas warm colors are red, orange, and yellow.

Seems simple.

But then why do we call some whites “cool” and others “warm”?

And how can a lipstick be “blue-red”?

It’s enough to make you feel like the hapless Cinderella, unable to choose between cream and ecru dinner napkins.

The answer is:

Anytime you move towards blue on the color wheel, you get a cooler color. Anytime you move away from blue, you get a warmer color.

Let’s look at green, for instance. Green is between yellow and blue on the color wheel.

Cool green is blue-green

If you move towards blue, you get blue-green, which is cool.

(You also get evergreen and forest green, but I’m trying to keep this post simple. I’ll come back to that.)

Warm green is yellow-green

If you move towards yellow, you get yellow-green, which is warm.

What about blue itself: Is there such a thing as warm blue?

Yes. When blue moves away from true blue and towards yellow, you get green-blue, which is warm blue.

Wait a minute. Doesn’t that mean “warm blue” is the same thing as “cool green”?

Yes. Some colors are definitely “blue,” and others are definitely “green,” but the exact boundary is subjective and depends on context.

What about when blue moves towards purple/red?

In that case, the resulting color is not “warm blue;” it’s “cool purple.”

(As purple continues towards red, it becomes “warm purple.”)

Anyway, here’s a handy reference chart.

(I made this years ago in a pastel drawing class.)

Two things to note here:

1. All the colors have warm and cool counterparts except orange. Orange is always warm. Light orange is a “cooler” version of orange, but it’s still a warm color.

2. You might have noticed that I listed “teal sea green” on the warm side of this chart. But earlier, I said that teal and sea green are “blue-green”—cool green. Let me explain. (Although feel free to skip this part if you didn’t notice.)

It depends whether you’re looking at this color as “blue” (in which case sea green is warm) or “green” (in which case it’s cool).

Sea green can work with both warm and cool color palettes.

Again, our perception depends on context:

• In a warm palette, sea green appears blue next to leaf green, but “green” next to turquoise blue.

• In a cool palette, sea green appears “blue” next to evergreen, but green next to true blue.

So why is MAC’s Ruby Woo lipstick considered “blue-red”?

Because it’s a red that’s closer to blue on the color wheel. “Blue-red” is close to what we think of as “true red.”

(Consider that printers make red from magenta, cyan, and yellow, so true red must have more blue, aka cyan, in it than just magenta and yellow, which would make orange-red.)

If a red lipstick isn’t blue-red or pink-red (both cool), it’s orange-red (warm).

Why do we call some whites “cool” and others “warm”?

It’s true that there’s only one white—the absence of all color. The theoretical “true white” paint has absolutely no pigment in it. But this would result in harsh, glaring walls, which most people don’t want.

Cool white is actually very light grey, blue, or green. Warm white is very light beige, yellow, or orange.

(However, Cinderella was right to be confused. There’s no set-in-stone difference between cream and ecru.)

Now, go forth and throw a fabulous banquet with just the right napkins!