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Which Color System to Use for Postcard Design: RGB or CMYK?

April 8, 2014


Print still remains not only a valid and effective option for marketing, but with less competition in the mailbox, it gives small businesses a competitive edge. Not only are you able to attract new audiences to your brand, but a well-timed fast postcard direct mailing can bring those longtime customers coming back for another round. Still, to use print effectively you need to know what you're doing. Many a marketer has made the mistake of not fully understanding the way that print works and ending up with boxes of printed postcards that look ill-designed and not at all professional despite appearing great on-screen.

The problem: knowing the difference between RGB and CMYK colors.


When you look at almost any type of digital screen, what you're seeing is a projected RGB image. The basic idea is that your computer monitor is a blank slate and each color added to the projection is a combination of the three primary colors: red, green, and blue. For this reason, RGB is commonly called "additive." If all possible RGB colors are combined, the result on your screen is pure white. It sounds great in theory, but printing in RGB rarely ends well. Because you're likely using your computer to render your postcard image, you're probably working with RGB colors.


If RGB is "additive," then CMYK is the opposite - "subtractive." This simply means that instead of adding colors, the printing process is actually removing colors. Therefore, the absence of all CMYK colors on a white sheet of a paper would obviously leave a white color - the direct opposite of RGB. The four colors used in CMYK printing are cyan, magenta, yellow, and black.

The RGB/CMYK printing issue may seem like a relatively new problem - after all, computer monitors and digitally-aided graphic design have really only become widespread in the last few decades. However, back when printing presses were all the rage (you know, before we became tethered to our computers), it was well known that using an RGB palette simply wouldn't work due to the additive nature of the colors. To combat this issue, the CMYK model was introduced, thus creating a more correct palette and range of colors. With the early CMYK printing format, a key was used (the K in CMYK) to align the different color plates.

So, what's the best option for your direct mail advertising postcards?

The answer depends on what type of project you're working on.

If you're working on a postcard design that will always be digital, then the correct answer is RGB. Because computer monitors today have the ability to display millions and millions of colors, you'll have a wider spectrum with RGB and you can rest assured that your original vision will appear the same or similar on your screen as it does for other people who are also viewing it on a digital device. In short, think RGB for web design, e-postcards, or any other digital-only final product.

Now, if you want to print your own postcard, that's a completely different story. Anything that is intended to be printed will need to have a final product using CMYK colors for the best possible results. You have a few options depending on how you are creating the postcard image.


Adobe Photoshop may be the most commonly used image manipulator, but if printing is the end goal, you're going to need to do some conversions. Fortunately, it's pretty easy to accomplish. Build your image using the RGB standard and then when you've got everything the way you want it, convert to CMYK mode to create a printable product. Be careful not to go back and forth too much as the image quality will be degraded every time you switch modes.

Illustrator and Quark Express

With Adobe Illustrator and Quark Express, it's better to start building in CMYK as these programs are more for print design. If you're not sure you fully understand the concept of spot colors, it may be time to call in a custom postcards specialist to give a final polish to your project.

The differences between RGB and CMYK may be subtle to the naked eye, but the simple fact is that they matter. Getting it right could make the tiniest bit of difference needed to turn your postcard ideas for marketing into success stories.