The two most common color schemes are RGB and CMYK. An RGB color scheme consists of three colors: Red, Green and Blue. These three colors are projections of light that can be overlapped in millions of color-strengths and combinations to create on-screen colors and images. RGB colors are associated with television screens and computer monitors, but is not used in offset printing.
CMYK also has difficulty with dark reds. When dark reds are converted and printed, they have a tendency to print as dark browns. Like blues and purples, dark reds and dark browns have similar color percentages. Creating a dark red in CMYK requires 100% magenta/100% yellow/60% black. Creating a dark brown requires 70% magenta/100% yellow/80% black. To keep your dark reds from printing as dark browns, we recommend that you reduce the amount of Black in them.
The way that color is viewed on-screen can cause printing issues. A color will never print out to exactly to match its on-screen source. Colors vary from monitor to monitor, and different printers produce different color results. All these variables affect the printed outcome. To better avoid these problems, it is always preferable to view files in CMYK format. This will never be 100% accurate, but it will give you a better representation of your printed file.
When using RGB and CMYK, it is important that you design, view and upload your files in CMYK. Most programs will allow you to view your file in CMYK mode, and we have a list of instructions on how to use CMYK in most programs.Black:
Black can also be a problem for designers. This problem often occurs during RGB to CMYK file conversions, and is caused by RGB and CMYK's inability to recognize each others black values; a black color is represented as a "negative" value of "0,0,0" on the RGB color scale, whereas, a CMYK color scale represents black with a "positive" value (e.g. 75% Cyan, 40% Magenta, 40% Yellow, and 100% Black). This occasionally leads to a situation where a rich black color that was produced in RGB, is converted to a duller, watered down color in CMYK.
Unlike CMYK, that generates a wide variety of black color through variant values of cyan, magenta, yellow and black, RGB is limited to a single "0,0,0" value. This doesn't mean that RGB can't generate rich black colors, but it does mean that you have less control over blacks, when they are printed out, or transferred from file to file, and from program to program. Converting into a CMYK color scheme gives designers more control over the black color that is ultimately produced. They are no longer limited to the "0,0,0" value of an RGB black.
When creating blacks in CMYK, many designers make the mistake of setting the black on the CMYK scale to 100% and turning all the other color values down to 0%. This is not, however, the best way to create a "rich" black, and it will cause blacks to print in duller, less-vivid tones. To obtain a "rich" black color, we suggest that you set the CMYK value to: 75% Cyan, 40% Magenta, 40% Yellow, and 100% Black.
Commands in Major Software Programs to Convert Your RGB files to CMYK
Adobe Photoshop Image/Mode/CMYK
Adobe Illustrator File/Document Color Mode/CMYK Color
Microsoft Publisher 2000 Tools/Commercial Printing Tools/Color Printing/Process colors (CMYK)
Quark Xpress 4.1 Edit/Edit Colors/Show Colors in Use/Highlight Color and click Edit. Then change model to CMYK and de-select Spot color.