It's about harmonious colors.

Not all Shinkansen are white and blue.

Only the Tokaido Shinkansen is a real vehicle with a white background and blue edges. Other Shinkansen, even Yang Shan, which is directly connected with Tokaido, do not have such white vehicles.

It was only at one time that many Japanese dramas, such as love stories in Tokyo and love on the Shinkansen, were introduced to China. The shooting time of these dramas happened to be just when the 300 series running in Tokaido was born, and it was also the most advanced car on the Shinkansen (around 1995), so many places in these Japanese dramas used the 300 series as the background to symbolize the Shinkansen. In this way, when these Japanese dramas are played repeatedly in China, the image of the 300 series with white background and blue edges is deeply rooted in people's hearts, so that when many people talk about high-speed rail or Shinkansen, the first reaction in their minds is still the 300 series, and even many posters are still using the old 300 series as material when showing high speed.

So when we started to engage in high-speed rail, it was estimated that the diehards of the Ministry of Railways were influenced by those Japanese dramas and began to think that only blue stripes on a white background could reflect high speed, and other color schemes were not good, so all high-speed rails became "Donghai Road". In fact, the original painting of CRH5 blue painting is very beautiful.

As for why red and yellow are not used, it is because yellow is a special color for construction machinery, and red (especially big red) is difficult to identify in the case of low visibility, which is prone to accidents.