Citrus Red 2, Citrus Red No. 2, C.I. Solvent Red 80, or C.I. 12156 is an artificial dye

Dye

A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....

. As a food dye, it is permitted by Food and Drug Administration

Food and Drug Administration

The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...

 (FDA) since 1956 only for use in the United States to color the skin of oranges

Orange (fruit)

An orange—specifically, the sweet orange—is the citrus Citrus × sinensis and its fruit. It is the most commonly grown tree fruit in the world....

. Citrus Red 2 is listed as an IARC Group 2B carcinogen, meaning that it is "possibly carcinogenic to humans". However, it does not penetrate the orange peel into the pulp.

Properties

Citrus Red 2 is an orange to yellow solid or a dark red powder with a melting point of 156 °C. It is not water-soluble, but readily soluble in many organic solvents.