POP is Print Out Paper. You make a print by exposing the paper in contact with a negative to sunlight or UV light. It develops an image by reaction with the light, no developing needed. But the image is not really permanent. You have to tone it, or fix it or otherwise treat it to make it really permanent. The tone of the image looks like POP.
The image may look like an Ektachrome image because possibly the scanning of the print and saving it as a RGB file, to preserve the brown tone may have introduced some color artifacting.
pop can also have different colors sort of a "split" tone effect if the toning happens quickly and the excess silver isn't washed off completely first. Also if the gold toner is starting to be exhausted
Jamie