When the collar of a shirt or other garment differs in color from that of the body of the garment. The whole collar needs to be a different color, fabric or pattern. Do not use when only the frills on the collar are different. For dress shirts the collar is usually white with matching cuffs. This is then called a Winchester shirt. Sailor collars are almost always contrasting in color, thus tagging dress shirts, dresses and other garments is more useful.
