What is the Selection rule for colour in complexes?

Spin selection rule states that transitions that involve a change in spin multiplicity as compare to ground state are forbidden. 

(1) According to this rule, any transition for which Δ S = 0 (it means no change in spin multiplicity after d-d transition) is allowed. 

(2) If Δ S ≠ 0 (change in spin multiplicity after transition) then it is forbidden (transition not allowed)

Intensity of colour due to d-d transition:

(1) Intensity of colour due to d-d transition will found to be high if transition follow laporte selection rule.

(2) Intensity of colour due to d-d transition will found to be poor due violation of laporte selection rule.

(3) Intensity of colour in tetrahedral Complexes for (non centre of symmetry) is found to be higher than octahedral (centre of symmetry).

Important Note:

For first transition series d⁵ system, weak ligand field, and coordination number six (6) Complexes are found to be colourless due to violation of selection rule.

Related Question:

Although both [Mn(H2O)6]2+ and [FeF6]3- have a d5 configuration and high-spin complexes. But the dilute solutions of Mn2+ and Fe +3 complexes are therefore colorless. Why?

Which of the Complex of the following pairs has the highest value of CFSE?
Colour of Complexes due to charge transfer:
Why violet colour of [Ti(H2O)6]Cl3 disapear (colourless) on heating heating ? 
Why [Ni(CN)4]-2 is colourless while [Ni(H2O)4]-2 although both have +2 oxidation state and 3d*8 configuration ?
Why [FeF6]3– is colourless whereas [CoF6]3– is coloured ? 
Why Fe(CO)5 is colourless while Fe(bipy)(CO)3 is intensely purple in colour ?
Why all the tetrahedral Complexes are high spin Complexes ?