When planes were first built, white was actually not their original color and companies use over 65 gallons of paint to paint one plane, it’s just a simple science question, the main reason why aircraft are painted white is to reflect sunlight, and minimize both the heating and any potential damage from the solar radiation. It’s like putting your sun cream on, cooler plane mean cheaper cooling cost for airlines, and also helps in regulating the pressure in the plane at a cheaper cost, it doesn’t only drop down to cooling, most of the parts that are painted white are plastic, composite materials, carbon fiber, they are painted so that they don’t react with the atmosphere. This is why most of the planes are painted white.
We have seen planes with different color, now don’t get confused, some people like to have different color planes so they get it painted with different color, it not necessarily wrong to paint it with different color. Earlier airlines dint have any paint over them, so the problem is that those airplanes would start to tarnish over time, they had to spend time and money to polish them frequently, so most of the companies have chosen light-colored paint to paint their planes. This is all about planes being white.