Colors can vary in tone or hue. Hue is the difference in colors themselves (green versus blue), while tone is the degree of color (dark to light).
There are also the monochromatic colors of white and black. White and black can decrease or increase the shade, or richness of color, that you choose - in other words, adding white makes colors lighter and adding black makes colors darker. Making colors lighter with white is known as creating variations in tint, while making colors darker with black is known as creating different shades.
To learn more about color theory and how it applies to your photography join The Icon Photography School.
See also:
Color & Perspective
Color Simplicity
Analogous Colors
Complementary Colors
Color Wheel
Color Psychology In Photography
Color Balance and Highlight
Monochromatic Photography
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