Designers and artists all over the world use Pantone’s color guides to make sure their blue is actually blue. Like a Webster’s dictionary for color, Pantone guides are a standard against which anyone can check their own work.

Those standards are created at Pantone’s factory headquarters in Carlstadt, New Jersey. In this video, Quartz talks to the workers who maintain and enforce those standards.

One quality sets these workers apart: They have almost perfect color perception. Pantone actually requires all of its “color technicians” to take a color vision exam once a year. (You can take a version of the color test online, but Pantone says it’s not the same as taking it in person.)