What is the color of the sky?

The “sky" actually has no color, being that it consists of several colorless gases. The color(s) you see, mainly light to medium blues, are due to backscatter of sunlight in the blue end of the spectrum. Depending upon the position of the sun and of other items carried in the air (dust, smoke, smog, etc.), the color seen can be anywhere from slightly greenish to a orange-red to grey to anything in between. In fact, the more particulates between you and a sunset, the more colorful the sunset will likely become due to differential blocking of the blue end of the spectrum. A spectrum is a band of colors, as seen in a rainbow, produced by separation of the components of light by their different degrees of refraction according to wavelength.