The color of the bus makes it very noticeable, not only on the intercity route, but also in the city. It can be seen from afar both in summer and winter, and in the stream of cars, and on an empty road. At the same time, it is not too bright and does not distract other drivers. And the paint, which was produced on the basis of natural pigment, was inexpensive. Since there was little influence of natural aggressive environments on the bus upholstery, it was not necessary to repaint the paint too often.
Interestingly, not only in the USSR thought of painting public transport yellow. In the United States and now the buses that take children to school are of a conspicuous yellow color. And one of the brightest symbols of New York is yellow taxis. And in the USSR, even police cars were also yellow.