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Beginner's handbook

RGB vs CMYK: Guide to Color Systems

By on February 12th, 2019 Reading Time: 5 minutes

Imagine a color, any color. It could be bright and vibrant, or dark and dull. You’ve probably seen it somewhere, maybe in your favorite movie or on a cool poster hanging in your office. Combine enough colors and soon you’ve got a cool design. If you’ve ever wanted to put that design on something and sell it, you’ve probably done some tinkering in Photoshop.

The print file you get out of Photoshop and the image as it appears on your t-shirt might not be the same though. Often, the difference has to do with color systems, and why there’s a difference between how colors appear on our screens and how they look in real life.

In this post, I’ll go in-depth about one of the trickier color-related topics– RGB vs. CMYK color modes. I’ll break it down by answering some of the most important questions:

  • What are RGB and CMYK and when do we use them?
  • What is the difference between RGB and CMYK?
  • What is the most suitable color mode for printing?
  • Is CMYK better than RGB?

Let’s start with some basic color facts. All the colors we can see with our eyes are part of the visible color spectrum. They’re represented in the circle below.

visible-color

Visible color spectrum

Because of technological limitations, our computer screens and other similar devices can’t display every color that our eyes can see. Instead, display screens show colors in the RGB system.

What is RGB?

RGB stands for the three colors Red, Green, and Blue.  The system uses Red, Green, and Blue light to make new colors. You can see the RGB range compared to visible colors in the picture below.

rgb-color

RGB color spectrum

Each pixel in the digital devices we use has three tiny, slightly overlapping RGB light sources that trick our eyes into seeing just one color when looking from a distance.

So if you wanted to show something yellow, the RGB pixel would shine green and red light together, while leaving the blue one off. The stronger the light intensity, the brighter the colors appear. At full intensity, the combined colors appear white and at zero intensity they appear black.

What’s great about the RGB color system is that it gives you a wide of range color combinations you can play with when creating digital designs.

When is the RGB color system used?

RGB colors are used for digital purposes. Any images that appear on a digital screen will be displayed in RGB. This is important to remember when creating your print files since you’ll most likely do it in Photoshop or similar software.

If you’re Printful customer, we recommend you create your print files in CMYK and then convert them to RGB. I’ll explain the exact reasons later, but first, you might be wondering what CMYK is.

What is CMYK?

CMYK stands for Cyan, Magenta, Yellow, and Key (which is just another word for black). It’s basically the opposite of RGB; it uses colored ink to mask colors on a light background. This light background (usually white) reflects light, so each layer of ink applied subtracts from white light to make new colors.

For example, if you combine Yellow and Magenta (meaning subtract yellow from magenta), then you get Red. You can combine any two Cyan, Magenta, or Yellow colors to create one of the three RGB colors.

If it’s confusing, just try to think about drawing with colored pencils. If you combine two different colors, you’ll get a third. It’s the same idea behind CMYK.

When you combine all three colors, you get grey. Since we also need black, it’s the fourth color. This is also why CMYK is sometimes called the four color system.

Compared to RGB and visible color, the CMYK range looks like this:

cmyk-color

CMYK color spectrum

When is the CMYK color system used

CMYK is recommended for any printed material. This includes all of Printful’s products, from apparel to mugs, posters, and more.

Why do we use CMYK for printing? It has greater color accuracy, meaning even the smallest details and designs will look sharper.

What is the difference between RGB and CMYK?

Key DifferencesRGBCMYK
What does it stand forRed, Green, BlueCyan, Magenta, Yellow, Black
What's it used forDigitalPrinted
Variety of colorsLots of colors, vibrantFewer colors, sharper
Photoshop settingsDefaultMust convert from RGB to CMYK
Accepted print fileYESNO

I like to think of RGB as a lit match in a dark room, while CMYK is a picture of the lit match in the dark room.

With CMYK, color intensity is not as flexible as in RGB. It’s just impossible to replicate on ink paper or fabric the same intensity and brightness that a digital display can show.

This means some RGB colors don’t show up when printed in CMYK. The software you’re designing in (Photoshop and others) are set to RGB mode by default. That’s fine if your designs are only going to appear online, but printed designs need to be done in CMYK. You can read Printful’s Color Matching Disclaimer for more details about this.

Now, to answer the previous question of why you should design in CMYK and then convert to RGB for printing with Printful:

  1. We require files in PNG format. Only RGB allows you to export in this file, CMYK doesn’t
  2. When working in CMYK, sometimes (depending on the software) there can be issues if the file has multiple layers. The printer could print all of the hidden layers, making the final print look different.

To put it simply:

  • We accept PNG files
  • We want you to create your designs in CMYK so the colors stay accurate
  • Convert to RGB so you have a PNG file

How to convert RGB to CMYK

This depends on the software you use and which version you have, so I recommend finding a tutorial online for the software you have. Here is a short RGB to CMYK Photoshop CC tutorial.

Is CMYK better than RGB?

CMYK and RGB have different uses, and it’s important to know when to use which. Since we’re focusing on printing, we want to stay within the CMYK range. What happens if you don’t convert your RGB colors to CMYK?

Let’s take a look at this design as it appears in Photoshop:

cmyk-printed-example

Digital design example

As you can see, the colors stand out and the shadows are visible. Now let’s compare it to a printed t-shirt with the same design:

https://duw6wk4ou1qt.cloudfront.net/blog/wp-content/uploads/2019/02/comparing-colored-corrected-shirts.png

Not color corrected vs color corrected

Clearly, it doesn’t look the same. The t-shirt on the left looks flat and dull and hasn’t been color corrected. The t-shirt on the right matches the vibrant colors of the original design, it was color corrected.

You can see how much of an improvement this is. The colors stand out, they’re brighter than they were before and the printed version really captures what the original design was going for. You can also watch our color correcting video and learn how to do this for your designs.

So how do you avoid printing the wrong colors show up on your products? We recommend ordering color swatches. These are samples of different RGB colors as they appear on printed material. This will help you determine how to color correct for print. Watch our tutorial video to learn how to order color swatches.

Color swatches look like this:

https://duw6wk4ou1qt.cloudfront.net/blog/wp-content/uploads/2019/02/color-swatch-example.png

Printful color swatch example

They come on a black or a white t-shirt and have all of the different RGB colors printed to show what they look like in real life. They also come with the numbered color codes for Photoshop for you to manually adjust colors if necessary. You can download the digital files of the swatches below.

Download Printful’s Color Swatches

Combine your colors

Be brave and experiment with your color designs. Figuring out the right ones might take some work, but you’ll get there soon enough. Just remember these differences between RGB and CMYK and you’ll be a color expert in no time!

And don’t worry if you’re nervous about setting up your design files correctly, we’re more than happy to help you with that as well. Feel free to contact our Design Services team, they can assist you in navigating this sea of color.

You can find me devouring the dusty marigold pages of my First Edition Wheel of Time collection while enjoying a plate of fluffy pancakes next to my adopted goldfish, Harold.

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    1. Filip Pejanović Post author

      Hi Serge, you can download a digital file of the swatch values from your Printful account. Go to Printful dashboard > New Order > Select your store > Create a sample order > Add product > New Products > Choose any product > Upload file > Choose file > Click the “Download” icon.

      1. John Kirkham

        Or to put it another way, no. Those files are there (hidden in that weird complicated place) and they do help, but it would be way more helpful to have colour palettes that could be loaded into illustrator/photoshop. Everybody wins if you make it easy for your customers to use colours that print well.

        1. Filip Pejanović Post author

          Hi John, thank you for the feedback, it’s a good idea that we’ll add to our to-do list! As a temporary fix, you can download the digital versions of the swatches at the bottom of the article.

  1. Jason

    Thanks Filip. Very helpful, including the swatch download. (Now I won’t have to carry around my cut out T-shirt samples, since I travel a lot!) But quick question. Assume we’re building in Illustrator, in RGB already, and we’re using “fills” of backgrounds created from the RGB colors you specify. Then exporting as PNG directly from illustrator. That workflow should already be color correct, yes? (Essentially, there’s not CMYK in this process, as it’s all built from RGB colors based on your exact color specs…)

    Thanks! -Jason
    @thenomadexperiment

  2. Tj

    Thank you for the article. I much prefer this format rather than the instructional videos. I do have a couple of questions though.
    Is the PNG file the only file type that is accepted?
    If so, why? If you are converting these files back to a CMYK format, why not accept vector files already in CMYK?
    I am grateful for the electronic color swatch samples and for the printed versions. I found it difficult to find and order them. The links for the white shirt, black shirt, etc. were helpful but once you click on one and start the order for it you cannot get back to those links to easily put one of the other products in the same order. I still don’t know how to order one of the swatch samples without using those links.
    Wouldn’t it be helpful to have a swatch sample matrix that shows these RBG colors with their closest CMYK colors? As it is, if there is any depth to the design you are creating, it is a lot of work to have to go back and color correct into RGB values when you know that you are going to turn right around and turn it back into CMYK.
    Thank you for your time and assistance.

    1. Filip Pejanović Post author

      Hi Tj, thank you for the questions and the feedback, always nice to read that the article was helpful.

      Yes, please send us PNG files. This is to make sure there aren’t any layering errors when working in Photoshop. Sometimes our machines can print the hidden layers and cause the design to turn out differently.

      As for the color swatches and color correcting, you make a good point and I understand that the process can be tricky, we are working on streamlining this and making it easier for our customers to use.

  3. Michael Doyle

    Before reading this information, I sent along flattened PSD files in Adobe RGB (1998) to be used in my posters. I had previously used a wide-format Epson printer using Epson UltraChrome inks. The results were excellent. Is it OK to use Adobe RGB (1998) settings for my Printful poster files? Or is there a preferred RGB profile? Should I resend my files as PNG files or would my flattened PSD files be OK?

    Thanks

  4. Valeria Ferreira

    Hi there, please I am creating simple black text and according to the swatch palette, I should use RGB 39,37,37. I have created a sample print file with the mockup generator to compare and the file comes out RGB 51,36,37, which looks a better black. Is there any specific rule for black print colour on mugs and T-shirts. Thank you very much.

    1. Edward Zarins

      Hi there again, I misunderstood your comment at first. Sorry about that. For true black color you should use RGB 0:0:0. 🙂

    1. Giedrė Kronberga

      Hi Amir, just click on the text “Download Printful’s Color Swatches” and it will be with you in no time 😉

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