Blue stop signs do exist, but they aren’t issued or recognized by the U.S. Department of Transportation for use on public roads. Instead, these signs are typically found on private property, such as gated communities, university campuses, large parking lots, or privately managed roads. While they don’t carry the same legal authority as standard red stop signs, they serve an important function in regulating traffic and ensuring safety in areas not governed by public traffic laws.

Historically, the color of stop signs has evolved. In the 1910s, stop signs were yellow with black lettering because those colors were more visible at night under early lighting conditions. It wasn’t until the 1950s that red became the standard color for stop signs, largely due to its strong association with warning and danger. Advances in reflective materials also made red signs more practical and visible, even in low light.