Is there a comprehensive overview of food colors?
The EU has a list of food additives in which everything is given a number (so you don't have to deal with companies trying to hide things using alternate names):


https://webgate.ec.europa.eu/sanco_foods/main/?sector=FAD


Many of the colorings are under Group II and Group III, but many other items (eg, fruit and vegetable juices) can be used as coloring, so you can't just look in those categories.