Food colouring

A food coloring is a substance that is added to food to change its color. People tend to associate certain colours with certain tastes, so manufacturers add colouring to a product to build this association. They are also used for colours that seem natural or 'correct' , such as tomato ketchup. Foods that may not be obviously coloured may still have colouring to make them seem correct. Some common colouring sources:
Annatto is a reddish-orange dye made from the seed of the Achiote.
Chlorella is green, and derived from algae.
Cochineal is a red dye derived from cochineal insects.
Beet juice, turmeric, saffron, paprika are also used as colorants.
Many synthetic colourings are made from coal tar and coal tar derivatives, this causes concern about cancer and contamination.