It is a federal law.
because they feel like it
Visibility and distinction. It's a highly visible colour, and it's distinct in that it is the colour associated with school buses.
I think school buses are yellow because not many cars are yellow so they will stand out more. School buses are painted chrome yellow for its high visibility Also because the federal safety people say it has to be. So technically yellow school buses are a federal law
really school buses are orange and yellow
Not all buses are yellow but most school buses are yellow.
to be sure that it is seen
Yellow became the colour for school buses in 1939, so till then and for a while after 1939 it is conceivable that buses were a different colour than yellow.
According to a New York Times article (http://www.nytimes.com/1992/06/17/us/cooling-and-safety-trend-for-buses-white-tops.html), bus tops are painted white to help cool the interior temperature. "Painting the bus tops white dropped the interior temperature an average of 10 degrees during the summer, with as much as a 17-degree difference at peak hours. Wintertime temperatures were lower by only 3 to 4 degrees. The study also found that children behaved better on buses in cooler temperatures ..."
What state are you referring to? What is meant by "not repainting?" As long as the name of the school or school district is painted out and the warning lights and clear flashing strobe light are not operational, there is no nationwide law that former school buses be re-painted from their normal yellow color.
Yellow.
Yellow with black.
School buses are painted in a variety of shades of yellow or orange. But the official color in the US is called National School Bus Glossy Yellow (CMY 1, 12, 100). It is a mixture of cadmium yellow and cadmium orange, and was renamed from National School Bus Chrome, a paint that contained chrome yellowpigment (lead II chromate).