Not only do the colors help create a look that makes these look similar (similarity principle), but because they are all next to each other with similar patterns, visual aesthetics, and colors they can be grouped together. This can also be the similarity principle because they are all just similar enough in color and pattern to be considered one group.
Photo: Close Proximity
Photo by: http://kcb2007.blogspot.com/2012_04_01_archive.html
