evolution takes so long that yes in fact we would all be deadHere's how It should be done, if it were to be TESTED:
First adjust light to a specific spectrum, other than what plants can actually use, over 8000k or under 2000k, or in nano meters over 700nm or under 300nm
You must grow both male and female cannabis seeds together so they produce off spring. You use the seeds of the generation of plants before to grow new plants. Continue for several years... Seriously... Autoflowering strains would be the best, because they would reproduce several times within one year.
My HUNCH is that the plants will, some where along the line, realize that their environment has changed and that they must adapt to the new type of light available and produce primarily the accessory pigments, thus changing the appearance of the plants color.
Only one problem, if it is successful this strain of cannabis can never exist in nature, and can only grow in the type of light it has been adapted to.
A freak plant...
It could even produce new cannabinoids...