Why were old 3D glasses almost always red and blue (and not, say, green and orange)?

Question

I know how old 3D glasses work, but I want to know why they were blue and red rather than two other colors opposite on the color wheel. My guess is that red and blue cellophane or inks were cheaper when the technology/technique was developed, but that’s only a guess. (I know how 3D glasses work and only want to know why those particular colors were popular or nearly universal.)

In: Technology

Answer 1

Red and blue are on the opposite ends of the visible spectrum, green falls somewhere in the middle. The (comparatively) large frequency gap between those colours makes for better quality 3D images. Gives it more contrast I think, less colour overlap. Not an expert.