Why are red, green, and blue the three colours in a TV set? I don't understand!?

Question: I was learning in class about how the colours are red, blue, and green as well as black and white. I just can't understand why yellow isn't used instead of green. Blue and yellow make green and nothing makes yellow. So how come we can see yellow at all? Please help!

Answer: This is going to get a little complicated. There are two sets of primary colors: the additive primaries, and the subtractive primaries. When you work with additive primary colors, you start with black, and add light in the additive primaries to get to any color up to white. When you work with subtractive primaries, you start with white light, and filter or remove the colors from it (as with pigments or paints) to get to any color down to black. The additive primaries are red, blue, and green. The subtractive primaries are cyan, magenta, and yellow. These are the actual primary colors you would use in paint, although a lot of people mistakenly call them blue, red, and yellow. Since the TV screen starts out black and lights up, the pixels are red, green, and blue. If just the blue dots light up, you get blue, and so on. If the red and green dots light up, you see yellow; if the red and blue dots light up, you see magenta; and if the blue and green dots light up, you see cyan. If all three light up you get white. Conversely, with pigments, if you mix cyan and yellow you get green; if you mix magenta and yellow you get red; and if you mix magenta and cyan you get blue. Mix them all and technically you get black, although since pigments aren't perfect it usually comes out looking sort of brownish. Edit: I see Gary is a faster typist than I am. :)

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