Why examiners (or teachers) use red ink to check homework or examination papers?

Why examiners (or teachers) use red ink to check homework or examination papers?

PROF WAQAR HUSSAIN

            

          It is reported to be started in the 1700s by clerks and accountants correcting ledgers using red ink in their quills, and then teachers adopted this practice. The reason behind using red ink was to see teacher’s comment easily on the page of student’s writing as student write in blue or black. And red coloured remarks or markings get prominence.