The term 'COLOR OF PRINTING PRIMARY' can be broken down into two crossword solutions: ERRATA (6 letters) and ENS (3 letters). ERRATA is a Latin word meaning 'MISTAKE' or 'ERROR', and it is often used in the printing industry to refer to mistakes that have been made in the printing process. ENS is an abbreviation for 'envelope size', which is a measurement used to determine the size of a printed document. Together, these two solutions indicate that the color of printing primary is usually black, as this is the most common color used in the printing process.