The chart was introduced in a paper by McCamy, Marcus, and Davidson in the Journal of Applied Photographic Engineering in 1976. The design consists of 24 squares with a black border. The aspect ratio of the size is approximately the same as 35mm film. The bottom row of squares consists of a gray scale, while the row above that consists of primary colors typical of chemical photographic processes (blue, green, red, yellow, magenta, and cyan). The other colors of the squares were chosen to mimic natural objects such as skin colors, a blue sky, foliage, and flowers. The squares are supposed to have a consistent color appearance under a variety of lighting conditions as detected by color photographic film. These charts are also currently being used with digital cameras to ensure that a series of images are consistent in color balance.
One of the ColorChecker Classics by X-rite goes for around $80. They have also produced a mini version, a Digital SG version that has 140 squares, and a ColorChecker Passport which is pocket size and multi-positionable.
The ColorChecker has been spotted...
Photographer Erika Neola has the ColorChecker tattooed on her arm. She states, "Yes, the tattoo is real. No, it is not a Rubik's Cube."