IDK what the dyes were. I do know that they were rare earth complexes that were colorless under visible illumination. There was a tiny amount of image due to ambient UV, but when we turned out the room lights and turned on a fluorescent lamp directed towards the paper, it came alive like a flat screen TV in an age well before such devices.
At that time, we were working on metallized dyes for image stability and did get a whole series that were based on nickle complexes which is another story completely. In this case, a magenta dye would turn into a cyan dye upon contact with a mordant and a nickle salt. Thus, we proved that magenta did not exist!