In 1970, French writing utensil company Bic released the 4 Color Pen. Aimed at French schoolchildren, the chunky pen featured four spring-loaded cartridges providing black, blue, red and green inks.

The pen was a hit, and was exported to the U.S. the next year. It also saw strong sales here, with uptake by students, teachers, clerks, nurses and, I have to believe, designers who prized the ability to lay down multiple colors without needing to switch utensils. The product became so ubiquitous in America that I think most people didn't even realize it was a French invention.

Fun fact: The ball at the top was for dialing rotary phones.

As clever as the design was, it still bore the flaws of '70s thinking: The pen was sealed shut and therefore disposable. People tended to burn through the blue ink first, and then the pen was tossed, even though the other three colors still had plenty in the chamber. Bic later rectified this by providing a threaded barrel and selling refill cartridges.

Fifty-six years later, the pen remains a bestseller; Bic moves millions of these every year. Aside from the now-refillable cartridges, the only significant design change Bic made is that the ball has been replaced by a lanyard loop. (A touch-capacitive ball might've been more in line with the original spirit of the design, but I'm sure it'd be cost prohibitive.)

The pen was designed internally, and sadly, the industrial designer(s) behind it never received any credit.