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As a kid, I was taught that that blue and yellow make green, yellow and red make orange, and red and blue make purple - forming the subtractive color wheel. As an adolescent I was taught that blue and green make cyan, green and red make yellow, and red and blue make magenta - forming the additive color wheel. Somewhere in that time I was also taught that the colors of the rainbow are ROY G. BIV.
That last one is the only one that makes much sense to me in physics because perceivable light is not somehow a cycle, but rather a tiny segment of the EM spectrum.
Why do the colors at the top and bottom of the spectrum seem to be mixable? Is there anything in nature that indicates this should be the case? Is this just a psychological or physiological phenomenon?