"Green Smoke Alert" <- What is it?

What is a green smoke alert, and where does the phrase come from? Googling didn't reveal much but some green smoke grenades on Ebay... every damn search is monetized now.

I'm reading "Pit Bull," the story of Buzzy schwartz:

 

Euphemism - Green Smoke that goes up at Vatican when a new Pope has been selected.

Here's another Green ....... Shoe Option? That I haven't heard mentioned in a long while.

https://corporatefinanceinstitute.com/resources/knowledge/deals/overallotment-greenshoe-option-ipo/

 

Except the Vatican produces white smoke when a new pope is selected.

 

I thought it might be a Vietnam-war era idiom? A frantic call for a Huey/Medivac? Light off a green smoke grenade?

 

My first thought was something to do fire and/or carbon dioxide detectors. Flashing green lights usually have meaning. LOL

Then I searched... It probably has something to do with Schwartz's "red light/ green light" filter, which is nothing more than a 10-period EMA to determine bull/bear situations. also LOL.

 

Green smoke here in Colorado can only mean one thing.... : p

 

Green Smoke was a company that went out of business.

 

I think the green means the dollar here, and as it said, a run on the banks.

 

Does the book have “contact the author” info? The guy is retired, so maybe will be glad to talk to you about the past

 

There was a frat-type comedy movie back in the day, Eurotrip I think it was.... it had this funny af scene in it where they were on a tour of the Vatican and the two cats somehow got in the Pope's quarters. They caught his hat on fire accidentally from a candle and threw it in the fireplace... all of Rome saw the smoke and thought there was a new Pope. I forget how it went down, but as the room burned the one dude made it out on the Pope's balcony, I think he was wrapped in a drape or something.... he looked like the Pope... it was friggin hilarious.