Designer, architect and teacher Ted Naos created this interesting set of die-cuts. There are twelve colored, two white and two black ones in the set plus four other cards printed with information about color theory and the practical aspects of color and light.
The die-cuts, oddly, are not square but 3.75 by 3.5 inches and come in a plastic container similar to a CD jewel case, this can opened and used to display the color patterns you create. The idea is simple enough to create so you could create your own larger size version using thick colored paper and maybe cut out diagonal or oblong shapes. Thickish colored plastic could create some intriguing options because of its transparency.
This is just the kind of fun item found in art and design museum gift shops.