Red color of the spectrum does not scatter easily but it scatters at sunrise or sunset because when the white light or the seven light I.e. VIBGYOR coming from the space then it strikes on the Atmospheric particles during the sunrise and the sunset then, the color having low wave length gets reflect back I.e. VIOLET, INDIGO, BLUE and GREEN but the color having higher wave length, absorb by the particles as they have less energy and when the particles get excited then it scatter light of different wave length whose av wave length is equal to the color having higher wave length i.e. RED, ORANGE and YELLOW.
hope this answer will satisfy you