Question regarding colour
So here is another confusion in my mind.
I know that colours are a result of electromagnetic radiation in the visible spectrum interacting with our eyes. The visible spectrum consists of 7 colours, abbreviated VIBGYOR.
Now my question is, what are primary colours and secondary colours? And how come mixing of two colours produce an entirely different colour? I expected that all 7 of them would be primary. But that is not the case.
Also, for illustrating the real world scenario from which this doubt crawled into my mind, consider that i have two pieces of translucent films, one blue, and other yellow. Now initially i place the blue film in-front of a white bulb, then it filters all other colours other than blue. Now place a yellow in-front of the blue, and there, you have green. What is the working principle behind this? How come the "blue" light turned "green" after passing through the yellow film?