Which artificial dyes are forbidden by most countries of the world? Dangerous six?

it depends of concentration.

But in reglamentation1333/2008 from European Union about the list of food additives, E123, E127, E160b, E173 and E180 cannot be selled directly to consumers, it is only valid to sell it to food industry and not directly to consumers, so i think those are possibly the most dangerous. Furthermore in Spain  Red2G, BrownFK and Cantaxantine.