Why CoCl4 2 shows a deep blue colour?

Answer 1

because of spin allowed d-d laporte allowed transition

Answer 2

The deep blue color of CoCl4 2 arises because of the absorption of light in the visible region of the spectrum. This absorption occurs due to the presence of unpaired electrons in the d orbitals of the cobalt ion, leading to electronic transitions that give rise to the blue color.

Answer 3

d-d allowed laporte transitions