According to Chan, the rainbow has six colors -- red, orange, yellow, green, blue, and purple, in that order. (Yes, Chan knows that some people consider "indigo" a seventh color, but Chan thinks that's all nonsense.)
Chan wants to design a vertical tricolor (a flag with equal vertical stripes of three different colors) for Math Club, similar to this:
If Chan uses only rainbow colors, and also insists that the three colors appear in red-to-purple rainbow order from left to right (as in the example flag above), then how many different tricolors are possible?
