How to Convert Files Between Different Color Modes

CMYK, RGB, and Spot Colors Explained

First, here’s a short terminology lesson you can use to impress your graphic designer friends:

Color models:

Define colors using math. RGB and CMYK are both color models.

Color space:

A way of cataloging and organizing colors. Spot colors are a color space. CMYK can be a color space as well as a color model. Color spaces that use RGB include sRGB, Adobe RGB 1998, and ProPhoto RGB.

Color gamut:

The colors a specific device or printer can recreate, based on its technical capabilities. CMYK is sometimes used to refer to a color gamut.

Now we’ve covered that, here’s a quick breakdown of these three terms.

CMYK

CMYK is used for printing images with a lot of color, especially photos. It’s a color model that combines four primary colors – cyan, magenta, yellow, and black (key) – in different proportions to make thousands of other colors.

You’ll see CMYK expressed in percentages of each color. For example, C20 M50 Y10 K5 makes a light lavender. CMYK is printed as lots of dots, called halftones, which our brains interpret as blocks of color. The percentages can determine either the size or the frequency of each color dot, depending on the type of printing.

CMYK is a subtractive color model: to make lighter colors, you use less ink (have lower percentages), since this ensures that less light is absorbed and more light is reflected, so the color appears lighter. White in CMYK would be 0% for all colors. Technically, you can create black by having cyan, magenta, and yellow all at 100% – but printers wanted a purer black, which is why there’s a separate black ink.

RGB

RGB uses the same logic as CMYK – combining primary colors to create a wide spectrum of colors. However, RGB is for light, not ink, so it uses red, green, and blue, and it’s an additive color model. The more light you add (the more of each color you use), the lighter the color you get. When you have all three colors at full blast, you get white.

RGB is expressed by assigning a value between 0 and 255 to each color. So R255 G0 B0 would be pure red, R0 G0 B0 is black, and R255 G255 B255 is white. You’re probably encountering RGB right now, since it’s the color model used for screens. You may be familiar with RGB in the form of hex codes, which use hexadecimal numbering to translate RGB into code computers can read.

Spot Colors

Spot colors are a color space — a way of cataloging colors — specifically for printing and manufacturing. The most famous spot colors are Pantone colors: a proprietary system used to identify certain colors using numbers. The point is precision. Instead of saying to a printing company, “Please print this in a glamorous red,” and hoping for the best, you can say, “Please print this in Pantone 180 C,” and know exactly what you’ll get.

However, unlike with CMYK, the printer itself isn’t going to do the hard work for you! Spot colors are premixed to precisely match the specific color. Which is why you usually use them for projects that only use a few colors, such as in screen printing or pad printing. You would probably also use them when you have to be very precise, such as when printing brand logos (which usually only use a few colors.)

By the way, the fact Pantone uses numbers can make it seem like each color has been mathematically calculated, like RGB and CMYK colors. But it’s just a way of organizing the colors. They could have used names, letters, or intricately detailed pictures of exotic birds. Numbers probably just seemed easiest.

How to Convert Between CMYK, RGB, and Spot Colors

If you have Adobe Illustrator or PhotoShop, you can use these programs to convert a file from CMYK to RGB (and vice versa) automatically. There are also online converters, although these require you to upload an image, so be wary of sharing anything you would prefer a stranger on the internet not see or steal.

You used to be able to convert files to spot color in Adobe programs too. However, Adobe and Pantone (the dominant spot color provider) had a falling out in 2021 that resulted in Pantone colors being removed from Adobe programs. As of now, Adobe users need to pay Pantone an additional subscription to access Pantone colors in Adobe. There are unlicensed plug-ins as well as online converters that claim to convert Adobe files to spot colors.

Why It’s So Hard to Accurately Convert Between CMYK, RGB, and Spot Colors

Since all of these produce colors using different techniques, the actual colors you can make using them vary.

It’s like if we both decided to make our own paints, and you made yours by mixing state-of-the-art chemical pigments and dyes, while I was using only 20-year-old broken crayons I found in the bottom of a drawer. It would be hard for us to both make paints that were exactly the same color. And while you might be able to tinker with your fancy chemicals long enough to reproduce a version of my crayon tones, I probably wouldn’t be able to make a paint that came close to your most vibrant colors.

To understand how one type of color will translate into another, you have to look at color spaces. CMYK is a color space (as well as a color model!) Spot colors are a color space. Color spaces that use RGB include sRGB, Adobe RGB 1998, and ProPhoto RGB.

Think of color spaces as a practical application of color models. It’s nice that you can create thousands (if not millions) of colors using a color model, but that’s almost too much choice. So you use color spaces to organize colors within a color model into a more manageable range.

For example, sRGB and Adobe RGB 1998 are both color spaces that use the RGB color model to make their colors — but sRGB uses a smaller range of RGB colors than Adobe RGB 1998. This is because sRGB (standard RGB) was designed to meet the needs of most web users, who don’t need to be able to view that many colors, whereas Adobe RGB 1998 was designed for photographers working online.

Unlike my crayon analogy, none of the color spaces I’ve mentioned are inherently better or worse than the other. It depends on your purpose. The reason sRGB became the standard color space used on most computers is because most devices are capable of accurately producing sRGB — it’s within their color gamut. To experience the additional benefits of Adobe RGB 1998, you need a fancier computer, so it’s become more niche.

What Happens When You Convert Between CMYK, RGB, and Spot Colors

The more overlap between the color spaces you’re switching between, the better.

The CMYK color space is the smallest of our three, meaning that it has the smallest range of possible colors. The CMYK color space mostly sits within sRGB, but not entirely. (Remember, RGB is a color model, not a color space, so we’re using sRGB as the most common RGB color space.) So converting CMYK to sRGB has the most chance out of any conversion of being a good match – unless you use those forbidden CMYK colors. Trying to convert sRGB to CMYK is much harder, since there are many sRGB colors that don’t exist within CMYK. The device will guess as close as it can, but it won’t be a perfect match.

Meanwhile, CMYK’s color space sits entirely within spot colors, so it’s theoretically possible to create any CMYK color using spot colors. But that relies on the spot color system you’re using having an exact match. Picture Pantone cards as an example: You could easily come up with a CMYK color that Pantone hasn’t cataloged.

It’s a similar story for RGB to spot, and vice versa. The spot color space has a fair amount of overlap with color spaces that use RGB, like sRGB, but some spot colors fall outside it. So if your spot color design uses any of those colors, they’ll look very different when converted to sRGB. And going the other way, RGB color spaces use colors that don’t exist in the spot color space – and even if they do, you’re relying on your particular spot color gamut to have a color that matches your exact sRGB color.

The Bottom Line

CMYK, RGB, and spot colors all give you access to their own sets of colors, which means that a color you find in one might not be in another one. To understand how your colors will look when you switch between media, it can help to understand where their color spaces do and don’t overlap, and the color gamut your screen or device has access to. You can use online tools to automatically convert — but you might not get a like-for-like match.