Consider the installation on the right in the picture above. If we label each color with a number, then each square represents a permutation. Each square is now grouped into a group of 4 squares, as shown below. Each group has an interesting property. If you superimpose any two of the squares in the group, none of the colors will collide.
Now if we represent each permutation as a vertex of a graph such that two vertices are adjacent iff they collide. Then the largest independent set in the graph is of size 4. There are 4! = 24 such possible independent sets (order dependent). And all 24 groups are shown in the art installation.
