Sunlight has 6 colors. These are purple , blue , blue , green , yellow , orange and red. When light reaches the earth, it is exposed to fine dust particles and various gas molecules. The greater the wavelength of light at the time of scattering after the incident, the more light is scattered. According to him, purple light is supposed to be the most diffused. But the ozone layer of the atmosphere absorbs most of the sun's purple light. Excluding the purple light, the light of the left wavelength is blue. As a result, blue light is most diffused in the atmosphere. So during the day we see the blue sky.