Neuromancer, published in '84, famously opens with the line
The sky above the port was the color of television, tuned to a dead channel.
I've always interpreted this to mean "gray", if not literally "TV static snow", because it was what TV sets displayed back then, and also because it fits the mood of the novel. I'm well aware TV sets have changed multiple times the way they display a "dead channel": bright blue (Neil Gaiman jokes about this in Neverwhere, paraphrasing Neuromancer), black with a "no signal" message, going full circle to today's simulated "TV snow".
My question is, what did Gibson actually intend us to see? Like I said, I though it was a gray sky, but a friend told me Gibson was thinking of even older TV sets, from before the first "gray static" era, which displayed... what? Dark blue? Black? Plain gray, without snow? Unfortunately I cannot find any references for my friend's claim.
Note this isn't a question about tech (so answers focusing on the TV tech of the 80s or 60s probably won't answer the question), but about the imagery Gibson was actually trying to evoke. Is there any reference, like an interview, answering this?