Teachers have used the dreaded red pen for years and still do to mark papers and grade someone’s school work. It’s a powerful pen. Its influence reaches beyond the school classroom. We use red ink for ...

There is no such thing as “black light wavelength”—so why do black T-shirts, black crayons, and black marking pens look black ... which stands for red, orange, yellow, green, blue, indigo, and violet.

Reviewed by Pamela Rodriguez Fact checked by Yarilet Perez Signing your name on a document or check seems like a pretty straightforward process. So does endorsing a check for a spouse or child who's ...