Non-soluble artificial color. Also called Allura Red AC, FD&C Red 40, E129, Food Red 17. See http://en.wikipedia.org/wiki/Allura_Red_AC
Food coloring is usually water soluble, these are the non "lake" versions of the dyes. When a non liquid is dyed the dye needs to be altered slightly to make it mix better, thus the "lake" version.