1) Color space 
In offset printing, a spot color is any color generated by an ink (pure or mixed) that is printed using a single run. The widespread offset-printing process is composed of four spot colors: Cyan, Magenta, Yellow, and Key (black) commonly referred to as CMYK. More advanced processes involve the use of six spot colors (hexachromatic process), which ...
The technique of coloring for emphasis some areas of basic black-and-white advertisements, usually with a single color.
Solid and halftone dot printing of specific ink colors. Generally used for cartoon type designs with broad coverage of inks.
Use of one additional color in printing.
Small area printed in a second color.