Why educational institution buses are in yellow colour?

School bus yellow is a color which was especially formulated for use on Canadian and United States school buses in 1939. The color is now officially known in Canada and the U.S. as National School Bus Glossy Yellow and was originally called National School Bus Chrome. The pigment used for this color was for a long time the lead containing chrome yellow.[1]

In April of that year, Dr. Frank W. Cyr, a professor at Teachers College, Columbia University in New York organized a conference that established national school-bus construction standards, including the standard color of yellow for the school bus. It became known officially as "National School Bus Chrome." The color was selected because black lettering on that hue was easiest to see in the semi-darkness of early morning.