1. A water-insoluble dye that is applied by reducing the dye to an alkaline form, applying the dye, then regenerating the insoluble dye by oxidation in the material; used for dyeing cotton
   "vat colours are known for their excellent colour fastness and are often used in dyeing denim"; "vat colours are known for their excellent colour fastness and are often used in dyeing denim";
   - vat dye, vat color [US]

Derived forms: vat colours

Type of: dye, dyestuff