When working in Adobe Illustrator you can choose between CMYK and RGB color. Which should you choose?
The easy/quick answer: Use CMYK whenever possible.
Its helpful to know:
CMYK (Cyan Magenta Yellow Black) is a color model intended for color printing. Its a “subtractive” color calculated for “reflection”.
RGB (Red Green Blue) is a color model for monitors, TV screens, etc, and is a “additive” color calculated for “emission”.
RGB is capable of a greater color spectrum, but is only fully utilized via your computer monitor. Not all RBG colors print well. CMYK is more limited, but images created/edited to CMYK print accurately according to what you see on your computer monitor.
Because Vector images are prefered for printing, its best to create your vector images in CMYK (especially logos). Of course, if your only designing for web/digital display purposes, then definitely utilize the broader capability of RGB.
Below is an example of an RGB image converted to CMYK. As you can see, color accuracy/quality is lost.
I intended this illustration to be used for Web purposes, so I utilized the RGB green that CMYK is not capable of. In this case, the difference is vast.