Unity

Monochromatic- The use of one color and its values. Staying in the same color range.

Arh, Luka. Study 17. 2011. DeviantArt. Web. 5 Dec. 2012.
<http://luka87.deviantart.com/art/Study-17-215711162?q>.

In the image above, the main color is a bronze while the other colors are simply a different shade of bronze.

Proximity- Simply putting elements together.

Snatch. 2008. DeviantArt. Web. 5 Dec. 2012.
 <http://omen2501.deviantart.com/gallery/?offset=24#/d1k9cax>.

As you can see above, most of the elements are placed near each other, drawing the eye from one subject to the next and giving it an finished appearance.

Analogous Colors- Colors that are next to each other on the color wheel.

Wei, Guan. To The End. 2012. DeviantArt. Web. 5 Dec. 2012.
<http://gworld.deviantart.com/#/d5l5vmg>.

In the image above, the use of reds, yellows, and oranges are all examples of analogous colors.