RGB vs CMYK
Scanners, digital cameras, and computer monitors use red, green and blue (RGB) light to display color. Commercial printing presses print with cyan, magenta, yellow and black (CMYK) ink, called process printing, instead of RGB light, and therefore produce a different range of color. To print on a four-color press, all RGB files must be converted into CMYK color.
Certain RGB colors that you can see on your monitor or camera (in particular, bright vibrant colors) simply cannot be replicated with standard CMYK inks. These unachievable RGB colors are said to be “out of the CMYK color gamut.” When selecting colors for your print project, we recommend using CMYK color builds to avoid potential RGB conversion issues. You are more likely to notice color shifts when you use a solid, bright color as a background or fill
A highly useful tool for selecting reproducible CMYK colors is the Pantone Process Color Guide. This swatch guide displays over 3,000 colors with the corresponding color build and is available on both coated and uncoated stock. This is also being used when a new logo and corporate stationery is being produced, to ensure colour consistency over time
RGB lights combine to make white CMYK inks combine to create black
You can improve the color accuracy of your monitor through a process called calibration. If you have critical color concerns, consider consulting a Pantone Process Color Guide or a hard copy proof. Be aware that: Monitor types vary in how well they can display color and graphics. Generally, CRT monitors have the best color and resolution; flat and LCD monitors can have poorer color quality and limited resolution. Individual monitor settings such as brightness, contrast, frequency, temperature, etc. will also affect your color accuracy.