Why the Sky seems to be Blue?

The sky appears to be blue in clear atmosphere due to Rayleigh scattering of light. As light moves through the atmosphere, it hits the gas molecules which are much smaller than the wavelengths of the different colours of light. The subsequent result depends on the wavelengths of the different colours present in the light. Most of the longer wavelength lights comprising of red, orange & yellow light are affected little & pass through the gas molecules. But the shorter wavelength lights like the blue are mostly absorbed but very soon the absorbed light is given off by the gas molecules. The given off blue light is then radiated in all the directions & gets scattered all around the sky. As a result, some of this scattered blue light always enters the eye in which ever direction the eye is fixed towards the sky & so the sky looks blue. The molecules of oxygen & nitrogen in the atmosphere are mainly responsible for this scattering of light which occurs as the electromagnetic field of the light waves induces electric dipole moments in the said molecules. Rayleigh scattering of light can also occur when light travels in transparent solids & liquids but is most prominent in gases.

It might be a little complicated for u to understand this ...but sky being blue is related to physics...when the light comes from the sun different layers of the atmosphere refract it...and when sunlight is refracted it gets divided into 7 colors(thats the reason u see the rainbow)... Every color has a different wavelenght through which it get refracted and the color blue has short wavelength and the other colors which have longer wavelength than blue like red or yellow(as you stated) are scattered in all directions and dont appear to the naked eye....i hope you understood :)