Monochromatic Colors. A monochromatic color scheme uses one color, but 3 different shades of that color. Example: Light, Medium, and Dark Blue.
Triadic Colors. A triadic color combination comes from using 3 colors that are equally spaced (3 spaces) apart on the color wheel. This could be purple, green and orange or it could be blue, yellow and red etc.
Analogous Colors. You get an analogous grouping when you use three colors that are all next to each other on the color wheel. For example, blue, teal and green or green, yellow-green and yellow etc. This example was done using blue, green and teal-all colors next to each other on the color wheel.
(All information and color wheel content gathered from http://www.scrapmatters.com/.)