Sir Isaac Newton, 1642-1726
Inventor of Color Theory

Introduction

Colors are mathematically described in terms of their hue, saturation and brightness. Hue determines the chromatic property of the color (red, blue and yellow are different hues). Saturation describes how vibrant or dull the color is. Brightness describes lightness or darkness of the color. When you choose a color with a color wheel or camera in colorSutra you set the color's hue. The top slider adjusts the color's brightness and the bottom slider adjusts saturation. The matching colors are mathematically derived from hue, saturation and brightness of the chosen color.

Johann Wolfgang von Goethe, 1749-1832
Early work in Color Theory

Hues

Hues determine whether colors match or not. Brightness and saturation, on the other hand, do not effect color relationships. For example, blue and orange are matching hues, so you can change the brightness and saturation of orange and it will still match the original blue! You can test this with colorSutra: in display screen tap on the large swatch (this is the complementary color) and change its brightness and saturation. The resulting color will still go with the original chosen (background) color.

Johannes Itten, 1888-1967
Modern Color Theory

Color Families

You can think of a hue as defining a color family. For example: the orange color family will consist of all the shades and tints of orange. In other words, orange color family consists of the colors with the same orange hue and all the different brightness and saturation values. Colors within the same color family can create beautiful combinations--known to designers as monochromatic color schemes. To derive monochromatic combinations in colorSutra, simply select a color and adjust brightness and saturation with the sliders. The resulting color will belong to the same family as the original color.

Itten's Color Wheel is the
basis for colorSutra algorithm

White, Grey and Black

White, shades of grey and black make a special color family, because they are derived by combining all hues in equal measure. That's why white, grey and black are not on the color wheel. To select white, grey and black start with any color, move the saturation (bottom) slider all the way to the left and move the brightness (top) slider to select the shade.

Further Reading

If you are interested in color theory here are some excellent resources:
wikipedia
gentle introduction
technical introduction