Answer
Crystal field splitting causes the electron to undergo d–d transition by the absorption of energy. Hence, most of the transition metal complexes are colored.
Work Step by Step
According to crystal field theory, the degenerated orbitals of the metals are split into higher and lower energy levels in the presence of ligands because of the repulsion between the electron pairs in ligands and d electrons of the central metal ion. So, this crystal field splitting causes the electron to undergo d–d transition by the absorption of energy. Hence, most of the transition metal complexes are colored.
