ColorChecker

The ColorChecker Color Rendition Chart (often referred to by its original name, the Macbeth ColorChecker or simply Macbeth chart) is a color calibration target consisting of a cardboard-framed arrangement of 24 squares of painted samples. The ColorChecker was introduced in a 1976 paper by McCamy, Marcus, and Davidson in the Journal of Applied Photographic Engineering. The chart’s color patches have spectral reflectances intended to mimic those of natural objects such as human skin, foliage, and flowers, to have consistent color appearance under a variety of lighting conditions, especially as detected by typical color photographic film, and to be stable over time.

The ColorChecker chart is a rectangular card measuring about 11 × 8.25 inches, or in its original incarnation about 13 × 9 in., an aspect ratio approximately the same as that of 35 mm film. It includes 24 patches in a 4 × 6 grid, each slightly under 2 inches square, made of matte paint applied to smooth paper, and surrounded by a black border. Six of the patches form a uniform gray lightness scale, and another six are primary colors typical of chemical photographic processes – red, green, blue, cyan, magenta, and yellow. The remaining colors include approximations of medium light and medium dark human skin, blue sky, the front of a typical leaf, and a blue chicory flower. The rest were chosen arbitrarily to represent a gamut "of general interest and utility for test purposes", though the orange and yellow patches are similarly colored to typical oranges and lemons.

...
Wikipedia