CMYK vs. RGB: Why colors on screen differ from printed colors
平田提"The data showed a vivid blue, but when printed, it turned dark." This is a common story told by first-time zine makers. This happens because computer and smartphone screens use "RGB" and printing uses "CMYK," which are different color expression methods.
What is RGB?
RGB is a color expression method using the three primary colors of light (red, green, blue). When monitors and screens display colors, they combine red (R), green (G), and blue (B) light. This is "additive color mixing," where the more light you combine, the closer it gets to white. Everything you see on screen, such as in Zoom or Canva, is displayed in RGB.
What is CMYK?
CMYK consists of the three primary colors of ink plus one more. When a printing press expresses colors with ink, it uses four colors: cyan (C), magenta (M), yellow (Y), and black (K). Like paint, CMYK is called "subtractive color mixing" because the more you mix, the darker it gets, and conversely, it becomes white when there's nothing. This is what the "C, M, Y, K" on home printer cartridges refers to. Colors are expressed by layering dots called "halftone dots" of C, M, and Y inks, but because mixing inks doesn't produce a perfect black, black is represented by K.
・Related article: Differences between Offset Printing, On-demand Printing, and Risograph
Why colors change
RGB is for light expression, and CMYK is for ink expression. The range of colors each can express, known as "color space," is different. Therefore, even if a color is within the RGB color space (appearing bright on screen), if it cannot be expressed in the CMYK color space, it will appear dull when printed.
Additionally, because Word does not allow specifying a color profile, exported PDFs automatically remain in RGB. While printing companies automatically convert it, if you use many vivid colors, the result might be unexpected.
Solutions
While perfect matching is not possible, there are solutions.
For Canva: Select "Share" → "Download" → "PDF Print," and an option to set the color profile to "CMYK" will appear (a paid plan is required). This can reduce color differences to some extent.
For Illustrator: You can choose between CMYK or RGB mode when creating the file. Even after opening, you can select CMYK mode via "File" → "Document Color Mode."
For Photoshop: It's common to work in RGB and then convert to CMYK just before submission by going to "Edit" → "Convert Profile." After conversion, adjust any changed colors before saving.
・Related article: Choosing an App for Making Zines
Summary
In any case, the most reliable method is to "print a test copy before submission." Even if you work in CMYK mode, the monitor displaying it is still RGB, so there will be differences between the screen and the print.
Try printing not just on your own printer, but also at a convenience store or other external environment. This allows you to check without your environment influencing the result. If you feel it's "darker than expected," try adjusting the original data to be a bit brighter.
More than achieving a perfect color match, "repeated test printing" is crucial.
Another important thing to check before submission is the bleed. For information on bleed, please refer to this article.
・Related article: What is Bleed?
