In 1922, the American Association of State Highway Officials met to determine a standard design for stop signs, and that’s where they decided on the color—yellow. Wait, what? Yes, according to Business Insider, stop signs were yellow because they thought that would grab drivers’ attention. They’d also considered red, but there was no dye available at the time that wouldn’t eventually fade. By 1954, however, sign makers had access to fade-resistant porcelain enamel, and could finally start making stop signs the red color we recognize today.
In the early 20th century, stop signs actually weren’t any specific color or even shape. Understandably, the lack of standardization confused drivers, so the American Association of State Highway Officials convened in 1922 to select a standard design. This is how the octagon shape came to be. The AASHO wanted to choose a shape that even drivers coming in the other direction would recognize, so that they would know that the oncoming traffic had a stop sign. (Learn more about why traffic signs are different shapes.) They chose a yellow design with black letters, figuring the colors would grab drivers’ attention.