Colors On Demand (COD) method and system for preparing customized colors and producing individualized dyeing products automatically and promptly includes but is not limited to cosmetic dyeing products (nail enamel, lipsticks, cosmetic for eye region and hair dye), color pens as well as painting and dyeing products suitable to users' peculiar needs. Wired or wireless Intranet, Extranet or Internet in E-commerce environment is applicable to COD system. Based on color matching, selecting dyeing products and on-line payment mode through Web, the said system forms commerce mode of 'a combination of E-commerce and practical commerce'.