This may sound like a bizarre question, but when I was rewatching the classic 1984 mockumentary This Is Spinal Tap, I noticed something about this scene.
Nigel Tufnel: He just was like, a flash of green light, and that was it.
This struck me as sounding similar to the earliest descriptions of Avada Kedavra in the Harry Potter novels.
Harry first dreams of Avada Kedavra in Harry Potter and the Philosopher's Stone.
... then Malfoy turned into the hook-nosed teacher, Snape, whose laugh became high and cold — there was a burst of green light and Harry woke, sweating and shaking.
Over and over again he dreamed about his parents disappearing in a flash of green light, while a high voice cackled with laughter.
The spell is actually first shown cast in Harry Potter and the Goblet of Fire.
There was a flash of blinding green light and a rushing sound, as though a vast, invisible something was soaring through the air....
The question of where the green-colored flash for the killing curse came from has been asked before, without a really compelling origin coming to light. (No pun intended.) However, it occurs to me that Rowling might have been (unconsciously, probably) influenced by This Is Spinal Tap, if she had seen it.
So, it is known whether Rowling had seen the movie when she started writing the Harry Potter series?