I wonder if there's a dye for water that had a molecular charge that would remain "attached" to the water molecule, without being bound to it, in such a way that one could see the water vapor?

Probably not, as water is one of the most polar molecules out there, and if it has enough energy to break that bond and become steam, it's unlikely there's a more polar, light-absorbing molecue out there.

__________________
I am Mugs, of the Alien clan of Usa, Nordamerica, a Terran, of Sol.

Mine: "Perception isn't reality. It's merely an abstraction thereof, and quite often not a very good one at that."

Heinlein's: "Staying young requires the unceasing cultivation of the ability to unlearn old falsehoods." "Freedom begins when you tell Ms. Grundy to go fly a kite."