Sky appears blue due to scattering of colour have lower wavelength scatters less.scattering is due to the presence of dust particles  present in the appears red incolour  in morning and evening. at this time light has to travel along distance,since sun rises in east and sets in west.hereduring this time colours of smaller wavelengths will get scattered off and sky appears with colours of longer wavelength ie redcolour,planet is a nonluminous body ieit doesnot have its own colour and it reflect the light of sun