The Color Wheel
The Traditional Color Wheel
The traditional color wheel is used for paints and other pigments.

Primary colors:
red |
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blue |
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yellow |
Secondary colors: two primaries mixed together
orange |
(red and yellow mixed) |
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violet |
(blue and red mixed) |
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green |
(yellow and blue mixed) |
Tertiary colors: a primary plus a neighboring secondary
yellow-orange |
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red-orange |
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red-violet |
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blue-violet |
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blue-green |
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yellow-green |
Complementary Colors
Complementary colors are two colors which sit opposite each other on the color wheel.
blue & orange |
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yellow & violet |
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red & green |
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blue-green & red-orange |
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yellow-orange & blue-violet |
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red-violet & yellow-green |
The Photoshop Color Wheel
The Photoshop color wheel is based on the way colors are mixed in light, and therefore on a monitor screen.

Primary colors (RGB):
red |
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green |
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blue |
Secondary colors (CMY):
cyan |
(green and blue mixed) |
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magenta |
(blue and red mixed) |
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yellow |
(green and red mixed) |
CMYK and RGB:
Subtractive vs. Additive Color Models
CMYK stands for Cyan, Magenta, Yellow and Key color (which is black). CMYK is the color model used for printing presses. It is based on the chemistry of mixing translucent printing inks rather than paint. It is called subtractive because if you mix the three primary colors (cyan, magenta and yellow) together, you get black (in theory; in reality you need to added pure black ink to get real black.)
RGB stands for Red, Green, Blue. It is based on the way the light mixes on a computer screen. It is called an additive color model because if you add the three primaries (red, green and blue) together, you get pure white light.

