Why you ask?
Its all due to this:
It's called Comet Lulin and NASA is saying its green colour comes from the gases that make up its Jupiter-sized atmosphere. Jets spewing from the comet's nucleus contain cyanogen, a poisonous gas found in many comets and diatomic carbon. Both substances glow green when illuminated by sunlight in the near vacuum of space.
That's all very well, but I recall another green light linked to a comet.
"...the Earth's orbit passed through a cloud of comet debris. You can even believe it if you like -millions did....
....it was reported in the news-bulletins during the day that mysterious bright green flashes had been seen..."
The Day of the Triffids by John Wyndham
So while normally the_Weapon and I would drive up to the hills to check it out with the reflecting telescope.
Not this time.
Don't Watch the Skies.