Why did the architectural photography of the ancient city turn green in the later period?

It is easier to separate from the foreground. The reason why the architectural photography of the ancient city was changed to green later is that the fluorescent green used in the green picture is easier to separate from the foreground in the computer system. At the same time, this kind of color is bright, and it is not easy to produce black edges, which is convenient for later editing and adding computer special effects. An ancient city generally refers to an urban settlement with a history of more than 100 years, which is still well preserved or basically restored to its original appearance after repair.