Colorants (both dyes and pigments) are listed according to Colour Index Generic Names and Colour Index Constitution Numbers. These numbers are prefixed in Brazil and various other countries with C.I. or CI, for example, CI 15510. This abbreviation is sometimes thought to be CL, due to the font used to display the information. A detailed record of products available on the market is presented under each Colour Index reference. For each product name, Colour Index International lists the manufacturer, physical form, and principal uses, with comments supplied by the manufacturer to guide prospective customers.
For manufacturers and consumers, the availability of a standard classification system for pigments is helpful because it resolves conflicting historic, proprietary, and generic names that have been applied to colours.
Explanation of the Colour Index Constitution Numbers can be found at the Colour- index.org site in PDF format.