I would first like to apologize if this is a dumb question.
I understand the physics of color sufficiently well. You have an incoming photon that intercepts an atom, the electron on the atom, the electron gets excited to some energy level for a few femtoseconds, and then again goes back to the ground state, expelling another photon during the transition. The wavelength of the emitted photon is what you see.
The point of this inquiry is to understand what is the precise physics that disables us from using plastic as an illumination source.