I've been watching the '66 Batman series on the Hub cable network, and I've started to wonder something. A recurring trope on the show was for villains to use knockout gas that was represented as brightly colored smoke. It would spray out of the Penguin's umbrella or the Joker's lapel flower or whatever. And I'm wondering: how did they create the "smoke" effect? What was it made of? What gave it color? Was it really smoke or some sort of fine dust? Does anyone have any ideas about this?