Because the method selection rule chooses the most specific applicable method, if a method overrides another method, then the overriding method will have more specific types for the controlling arguments.
The initial state of the system, photon energy, angular momentum and other selection rules can help in determining the nature of the intermediate state.
The general selection rule for such a transition to be allowed is that the molecular polarizability must be anisotropic, which means that it is not the same in all directions.
In the isolated molecule, the transition is strictly forbidden by spin, symmetry and parity selection rules, making it one of nature's most forbidden transitions.
The momentum selection rule is therefore broken, and the plasmon resonance causes an extremely intense absorption in the green with a resulting beautiful purple-red color.