My recent thrift store purchase of a new but some years old made in New Zealand 55% cotton/45% polyester rugby shirt, black and white, has complete care instructions-machine wash-warm 40°C, wash separately, do not use bleach, dry without delay, dry inside out, may be tumbled dried-warm, warm iron(where applicable do not iron directly over prints), do not dry clean, cold water detergents not recommended as they may cause dye loss. Never seen that last caution before. Maybe another reason optical brighteners are included in big name detergents.