[coldcode]

When I was in college in the 70's we went to a Miller brewery where they told us about some blue liquid they poured into Miller High Life that allowed them to ship the beer in clear bottles instead of brown. It came in tanker cars full; they claimed the FDA didn't know what it was (don't think I believed them).

[kevinmchugh]

I don't know what they used in the seventies, but now they use hop oil extract. The extraction process eliminates the possibility of the skunking/lightstruck reaction. Most colorless glass bottled beer use that today, though not all. The green bottle beers mostly don't, though they're still susceptible to skunking.

[goldenkey]

Likely was just a kind of food coloring. Simply by changing the tint of the beverage, one can prevent absorption of a band of light.