The colors on each side of a Rubik's cube sold in the United States today are: Red, Orange, Blue, Green, White, and Yellow. Red and Orange are on sides opposite each other. Blue and Green are on sides opposite each other. White and Yellow are on sides opposite each other. The following picture shows how the colors are arranged.
I do not know why these colors were chosen. The logo on the puzzle in the picture uses the pattern that I mentioned.
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