Spot color.

A spot color is one ink, mixed to a named standard, printed from its own screen or press unit instead of being simulated with overlapping process dots. Printed as a solid it carries no halftone dots, so it cannot drift the way a four-color build does when gain stacks up across screens. Screen that same ink back into a tint and gain is in play again, and on a garment the bigger variable is the ink film left on the cloth and whatever sits underneath, so the same Pantone number over a thin white underbase reads darker and duller than the chip. That is the reprint a shop pays for: the ink was right, the underbase was not, and a batch mixed for one job is hard to sell into another.