On Sun, 31 Dec 2017 11:58:41 +0000, Harry Bloomfield wrote:

All rather puzzling, but I remember a TV
experiment from way back, where they tested B&W TV's to hint at showing
some colour. Anyone remember it?

Yes, it was shown that certain flicker rates caused the brain to 'see'
colour. An OXO commercial was shown and some people saw the gravy as
brown and some as purple. It didn't catch on.

--
TOJ.