I think you guys are underestimating the food dye appeal when you blame it on just advertising stuff, or just dumb kids, or whatever.
Humanity has been adding dyes to cheese and butters for what, like a couple hundred years? Not nasty artificial dyes, generally, but still. The point is that color has a big influence on how appealing a food is.
Its been this way since our simian ancestors developed red-green color vision and started going after riper fruits. You can still see it today in housewives carefully picking over the produce looking for just the right apple.
Not defending artificial food dyes, just pointing out that the desires they aim to satisfy are strong, primitive, and pretty much universal.