OKI C7550 Benutzerhandbuch

There is no one correct way to achieve a good color match between 
the document displayed on your monitor, and its printed equivalent. 
There are many factors involved in achieving accurate and 
reproducible color.

However, the following guidelines may help in achieving good color 
output from your printer. There are several suggested methods, 
depending on the type of document you are printing.

    

The guidelines for choosing a color matching method make 
distinctions between Red, Green, Blue (RGB) and Cyan, Magenta, 
Yellow, Black (CMYK).

Generally, most office documents you print will be in RGB format. 
This is the most common, and, if you do not know your document’s 
color mode, assume that it is RGB.

Typically CMYK documents are only used in professional Desktop 
Publishing and Graphics applications.