In paints the color red and the color green are complementary colors.
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These two colors share no common properties and it is not possible to make green turn into red.
Mixing red and green together cancels both colors and gives you a brown. There is no way to make green into red.
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It makes brown because red + yellow + blue = brown color and blue with yellow is green, so red and green is brown.
But you can see a demonstration of how with additive color red and green make yellow. Additive color (color with light) has a different color wheel than subtractive color. With photography it is important to understand additive color along with subtractive color.
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