Explain why we classify the main colors as:

>red, orange, yellow, green, blue, violet

instead of as:

>red, yellow, green, teal, blue, violet

Look at this image. The stuff that we call 'blue' is obviously two different colors, and there's basically nothing in the space between red and yellow except for a thin border. Orange should really be thought of as yellow-red. If you divide things in this way, the colors are also more consistently spaced if you chart them against their wavelengths.