They are used in the vast majority of foods and you can recognize them, just like preservatives, by their E numbers. You use them to simply give color to your product or to prevent original color loss. Color loss occurs due to exposure to moisture, light, air or high temperatures. Some food colouring are even used to protect the nutritional value and taste of the product.
At Natural Spices you can buy both natural and synthetic food colouring online. The natural varieties are the ones without an E number. You can easily find this on the website under the heading E-number free, or clean label. Clean means that the product has undergone few processes and has no artificial additives. It is a category that is growing in popularity. You can buy both clean label food colouring and variants with E numbers in different quantities.