[RightWhale]

Was the whole sky green or was it the trail of some reentering space junk?

[BenLurkin]

Saw a meteor or space debris while driving some years back.

It was 'preceded' by a prolonged green flash that lit up the highway and the hills on either side.

I thought someone had fired a flare until I leaned forward and looked out the top of my windshield. Then I saw the object itself shooting off white sparks and leaving an orange trail.

[muawiyah]

As the Sun sets in the evening you see blue sky turn into red sky. In between, in the blink of an eye, you may see it turn to green ~ it'll look like a streak of green light.

You usually don't get a good look at it in humid atmospheric conditions. The air has to be exceptionally dry, and that's probably a rare event in the vicinity of Singapore.