Why ocean & sky looks Blue & sunsets are orange ?

 The sky is blue because the atmosphere tends to scatter shorter wavelength i.e, blue light to a greater extent than longer wavelength i.e, red light. Blue light from the sun is scattered every which way, much more so than the other colors, so when you look up at the daytime sky you see blue no matter where you look. This scattering is called 'Rayleigh scattering'; the amount of scattering goes as the frequency of the light to the 4th power. By the way, this effect is most prevalent when the particles that do the scattering are smaller than the wavelength of light, as is the case for the nitrogen and oxygen molecules in the atmosphere.

 

 The Reason why clouds, milk, powdered sugar and salt are white is because the particles in these materials that are responsible for scattering the light are larger than the wavelength of light. Consequently, all colors of light are scattered by more or less the same amount. Much of the scattering in milk is due to the lipids (fat). If you take out the fat, the milk will not scatter as much light.

  

This is the reason why sunsets are reddish, When the sun is setting, the light that reaches you has had to go through lots more atmosphere than when the sun is overhead, hence the only color light that is not scattered away is the long wavelength light, the red.