What was the original color of stop signs?

The original color of stop signs was yellow.

In the United States, early standardized stop signs used a yellow background with black lettering. Yellow was chosen because it stood out well in daylight and remained easier to see than many other colors, especially before modern reflective materials became common. The octagonal shape also helped drivers recognize the sign, even when its lettering was difficult to read.

From 1924 to 1954, American stop signs generally retained the yellow design, although some versions used red lettering. The first Manual on Uniform Traffic Control Devices, published in 1935, helped formalize sign standards across the country. In 1954, the standard changed to the familiar white lettering on a red background. Red pigments and reflective sign technology had improved, making red more practical and visually distinctive for a prohibition requiring drivers to stop.

A common mix-up is assuming stop signs were always red because that is the only design most modern drivers have seen. The change from yellow to red happened in the mid-20th century, so historic photographs and older road signs may look surprisingly different. The octagon, however, remained the recognizable stop-sign shape.