All the halogens are coloured. The colours arise due to

Halogens are colored because it has low ionization energy. Due to this reason, valence shell electrons get excited to higher region or higher energy level. The amount of energy for excitation of electrons is different for different halogens. However, It absorbs radiation in visible region and emits the complementary color. Thus, the correct option is (c) absorption of light which causes an electron to jump from the ground state to a higher state.