3D red cyan anaglyph motivation

3d anaglyph red cyan glasses got me interested in science and especially optics. I made one with stationery for a comic either a us relative gave or I got .

I just now learnt the dark colour of both is when the flip color makes it dark..

It was invented only in 1891. So it was not obvious.. that person did some optics experiments and eye regions..

I will get it next week.. Had some at different times of life!