NOTE: for the full, updated article, please go here. This is an abbreviated (and non-updated version).

Being pretty self-taught as far as UI design goes, I’ve always wondered why so many articles and books talk about color theory and palettes. In my experience, using a “split complementary palette” is about 0% predictive of me making nice-looking designs.

I have another word for that sort of thing: useless.

So if color theory doesn’t provide a solid basis for color in UI design, what does?

Let me throw an opinion at ya’: color modifications. It’s the tweaking of color that counts.

Or, said another way: The fundamental skill of coloring interface designs is being able to modify one base color into many different variations.

Color variations…

Allow you to modify one theme color for basically any purpose in your UI (this is hugely powerful, and, as we’ll see, what apps like facebook are already doing)

for basically any purpose in your UI (this is hugely powerful, and, as we’ll see, what apps like facebook are already doing) Help you to predict what color changes will look good

Make color seem less subjective (“subjective” is often a word for “I haven’t figured out how it works” — and it’s a word you hear a ton when folks talk about color)

Are we cool? We’re cool?

Great.

Darker & Lighter Variations

One thing I’ve noticed across many great-looking interfaces is that they often have darker and lighter variations on a particular theme color.

You didn’t think that search bar was just a translucent black overlay, did you? Spoiler alert: it’s not. No opacity of black overlaid on that blue will give you the color of the search bar. It’s a variation picked by some other magic.

Or, here’s another simple example:

Even element states are variations on a color. This isn’t best described as “a palette of 3 blues”. It’s one blue with variations.

But this begs the question: how do you actually modify a color to get good variations?

Here are our two principles:

We’ll look to the real world for reference cues. Even though our interfaces are “fake”, we still copy like mad from the real world, because after decades of seeing things in the real world, we just expect light and color to work in certain ways. We’ll use the HSB color system. The short of it is: it’s the most intuitive color system with broad usage.

Real-World Color Variations

Alright, look around you. What “color variation” are you undoubtedly seeing two dozen instances of every time you glance around your room?

Shadows.

A shadow is a darker variation on a base color.

Photo by David Blaikie

Now let’s jump into Sketch and get our color pickers and figure out exactly what happens when a shadow falls on our coral wall.

Like I mentioned, we’ll be figuring this out in HSB.

Note: Monitor/image color profiles might make these exact measurements different for you.

The brightness moves down — OK, so that was pretty obvious. But hold up – before we go generalizing too much, let’s actually look at another example.

Photo by Matthias Uhlig

Do shadows work the same way in Cuba? We’re about to find out.

Alright, now we can compare and contrast. Notice a pattern?

When there’s a shadowed variation of a color, you can expect brightness to go down and saturation to go up. We just looked at this in two instances, but as far as I’ve ever seen, it’s a solid rule you can go by.

(Now hue is a bit crazier; we’ll come back to it)

The Rules

Let’s unpack these concepts a bit more.

Darker color variation = raise saturation + lower brightnes

If you look back to our facebook search bar example, you’ll see that’s exactly what’s going on.

The hue moves 1° out of 360°, which is practically a rounding error.

The saturation went up as the brightness went down. The reason the search bar couldn’t be an opacity of black overlaid on the base blue is because, in HSB, adding black is equivalent to reducing brightness. Instead, we want to reduce brightness while simultaneously adding saturation. Black doesn’t add any saturation to our color!

Lighter Color Variation = lower saturation + higher brightness

Now, being the discerning and erudite readers that you are, you probably guessed that the opposite transform that gives us darker variations will give us lighter variations.

And you nailed it, by golly.

Of course, we can go one step further. If we go on lowering saturation and raising brightness till the cows come home, where do we end up?

Here:

We end up at white.

You can think of making lighter variations as adding white.

The Most Important Thing

If you remember only one thing from this article, remember this:

Darker color variations are made by lowering brightness and increasing saturation. Brighter color variations are made by increasing brightness and lowering saturation.

With this simple idea, you will be able to do amazing things with just a single color.

The truth is, so many variations in color between elements — or even states of the same element — are just simple color modifications.

Here’s Harvest, the time-tracking app I use and love.

Look at the header. The hover state is lighter. The selected state is darker.

Or look at the green New Entry button.

The hover state is a darker variation — higher saturation, lower brightness.

You will use this again and again.

What About Hue?

To understand how to modify hue, we first need to understand that each color has a sort of “perceived brightness” to it — called luminosity.

Even though this blue and this yellow are both at 100% HSB brightness, which appears brighter?

I mean, like, ask anyone off the street: which is brighter?

“Um. Yellow. Yellow?”

Thanks, rando. You just discovered luminosity.

“So I’m right?”

Yes, yes you are. Even if you hold brightness and saturation constant, and just vary hues, you will get a range of luminosities, or perceived brightnesses, which we measure in values between 0 and 100.

Now, I’ve printed the numbers out for you, but chart’s worth a thousand numbers, right?

Look, Sherlock, a pattern.

And this particular pattern answers our question from above. Remember how we saw that sometimes, for a shadow, hue would shift down and sometimes it would shift up? Why does it do that?

Well, first, notice that this graph has three maximum points and three minimum points. The low-points are red, green, and blue. The high-points are cyan, magenta, and yellow.

Does these particular colors ring a bell? Yes. RGB and CMY are popular color systems, but ignore that for now, because it’s leading you astray.

The important bit is this: if you don’t count saturation and brightness, shifting hue towards red (0°), green (120°), or blue (240°) will decrease the luminosity, or perceived lightness of the color. And shifting the hue towards yellow (60°), cyan (180°), or magenta (300°) will increase the perceived lightness of the color.

The trick is to just make the movement of the hue match up with the movement of the saturation and brightness.

That’s why the shadow on the coral wall shifted down in hue — it was shifting towards red, at 0°, which is the nearest minimum point to 21°.

And that’s why the shadow on the teal wall shifted up in hue — it was shifting towards blue, at 240°, which is the nearest minimum point to 194°.

The Way of Color

So when it comes to color variations, ask yourself: do I need simply a lighter or darker variation on a color I already have?

(Hint: yes, probably)

Darker variations:

Brightness decreases

Saturation increases

Hue (often) shifts towards a luminosity minimum (red, green, or blue)

Lighter variations:

Brightness increases

Saturation decreases

Hue (often) shifts towards a luminosity maximum

This will allow you to take one hue, but modify it endlessly for all your UI needs, using darker and lighter variations where appropriate.

An interface with one color and many modifications

I just whipped together a quick example here. A whole interface being built out of a single color. Say… does that shade of teal look familiar?

Now I’ve been pretty brief with all of this. There are still many topics to cover:

How is hue even more important in gradients and data visualization ?

even more important in and ? When you’re in Sketch (etc.), what technique do you use to make darker variations ?

? Do you to move saturation or brightness more ?

? How do you find grays that match your color scheme?

that match your color scheme? How do you pick totally unrelated colors that look good together?

that look good together? How do you fix it when colors clash ?

? And, of course, just why are RGB and CMY the low/high points on the luminosity graph?

I’m glad you asked.

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