Question

When sunlight passes through the atmosphere,Which colour of light gets scattered strongly by the fine particles in air

Answer 1

off course color is blue
The color of scattered light depends upon the size of particles. 
   as you have to know, the molecules of air and fine particles present in the atmosphere have size smaller than  the wavelength of visible light. they scatter light of shorter wavelengths at the blue end than light of longer wavelength at the red end. that's why when sunlight passes through the atmosphere, the fine particles in air scatter the blue more strongly than other color.