National School Bus Yellow was officially adopted in 1939.
The decision came from a national conference on school transportation organized by rural-education specialist Frank W. Cyr at Teachers College, Columbia University. Representatives from the then-48 states met to establish common standards for school-bus construction, safety equipment, and appearance. One result was a distinctive yellow-orange paint color that would be easy to recognize.
The shade was originally called National School Bus Chrome, a name linked to the chrome-yellow pigments used in early paint. It is now generally called National School Bus Glossy Yellow in the United States and Canada. Its visibility, especially in low light, helped make it a practical safety choice rather than merely a branding decision.
A common mix-up is assuming that 1939 was the year a federal law mandated yellow buses nationwide. The 1939 conference established the influential standard, while modern requirements come through federal recommendations and state regulations. The color also has an official technical specification, Federal Standard 595a Color 13432.