Monochromatic

formal — A Monochromatic Color Scheme is created by taking any oneof the twelve Hues from the Basic Color Wheel and repeating it in various Tints, Shades and Tones.

Source —http://color-wheel-artist.com/monochromatic-color.html

informal— when one color is used from the color wheel

Analogous 

formal– Analogous color schemes use colors that are next to each other on the color wheel. They usually match well and create serene and comfortable designs.

source– http://www.tigercolor.com/color-lab/color-theory/color-harmonies.htm

informal– any one of a group of related colors that are near each other on the color wheel.

Complementary 

formal– Colors that are opposite each other on the color wheel are considered to be complementary colors.

source– http://www.tigercolor.com/color-lab/color-theory/color-harmonies.htm

informal– the colors those are opposite of each other in the color wheel

Triad  

formal– a triadic color scheme uses colors that are evenly spaced around the color wheel.

source– http://www.tigercolor.com/color-lab/color-theory/color-harmonies.htm

informal– three defined colors from the color wheel

Tetrad 

formal– A four-hue color system that is balanced based on either a square or rectangle inscribed in the color wheel.

source– https://www.pinterest.com/pin/18718154679331677

informal– when four colors from the color wheel