triad is a color scheme, a special variant of the split-complementary color scheme, with the equal distance between all colors.
The Tetrad color scheme is considered the richest because it uses four colors arranged into two complementary color pairs
Monochromatic color schemes are derived from a single base hue and extended using its shades, tones and tints.
Analogous colors are groups of three colours that are next to each other on the color wheel, and a tertiary. Red, orange, and red-orange are examples.
Split Complementary color scheme is a three-color combination consisting of base color and two colors that are 150 degrees and 210 degrees apart from the base color.