The presence of d orbitals is a common feature of Transition components.
The d orbitals split and become non-degenerate due to the various symmetries of the orbitals and the inductive actions of the ligands on the electrons (which have different energy levels).
Reason for the color of transition metals:
Transition metals, on the other hand, are unique in that the energy difference between non-degenerate orbitals corresponds to the energy of visible light radiation.
When the electrons are present in an octahedral metal complex, they can absorb green light and move from the orbital, the compound will reflect all colors excluding green color.
As a result, it is easy to identify the complementary colour of green, which will be the colour of the compound, magneta, by utilising the colour wheel.