What are those colored squares that you hang up?

The colored squares you hang up are often referred to as "color swatches" or "color samples." They are typically used in design and decoration to help visualize color combinations in a space or project. These swatches can come in various forms, such as paint samples, fabric swatches, or decorative tiles, and are used to make informed choices about color schemes. They can also serve as decorative elements in their own right.