As I've worked through this series I'm surprised every time I recolor a pattern (which is such an easy process in Illustrator that I create many, many, many colorways for each repeating pattern I make.) Changing the arrangement of the light and dark color values makes elements of the pattern recede, or disappear altogether. It ends up looking like two completely different patterns. I pulled out my favorite books on the subject, by Josef Albers and Johannes Itten.
It was interesting to read their theories and then to see them in action in the pattern.