That’s kerosene. Used in lighting oil lamps at that time, too.

(^From a draft of the script.)

Apparently, “kerosene in its natural state is a clear, colorless liquid. To comply with U.S. federal tax law, kerosene is dyed red.” [X] Idk what colors it came in Paris in 1860-5ish, when Louis burned down the TdV… 😛

The fact that it came in a keg like that, and that alcohol is flammable, one could easily mistake it in the movie for wine. So many victims bled to death on that stage, and then considering that Lestat had told Louis to pretend blood was wine, I think it makes sense that this kerosene is amber/red in the movie, figuratively, it seems to be blood or wine, even if that color might be wrong historically.