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
To understand this, you should understand how color works in your eyeball. You have 3 different color sensors in there called cones — these are cells that are stimulated by red, green, and blue wavelengths of light. Every color you see is some combination of your brain interpreting these 3 signals (yes brightness from rods is also in there if you want to get technical). A red filter basically blinds the red cones in one eye, and the blue filter blinds the blue cones in the other eye. What this does is make it so each eye is seeing a slightly different image. Your brain interprets this as the two images coming from different places, and is looks 3D. Ta-da!
Now, why not any other color on the color wheel? I’m going to do a bit of speculation and suggest that it is because red and blue block only those color receptors in your eye. An orange filter would block both red and green receptors, which wouldn’t be as effective at producing separate images for each eye. I suppose you could try red-green glasses, but then the effect would still not be as effective because the colors are not as far apart on the color graph as red and blue.
Check out the Physiology of Color section on the wiki here [wiki](https://en.wikipedia.org/wiki/Color_vision) for a graph.
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