I made the logic / color space behind that. There isn't actually 4, but that 4th one you perceive...Notice ex. search doesn't do this, it's a stubborn Android

I made the logic / color space behind that. There isn't actually 4, but that 4th one you perceive...Notice ex. search doesn't do this, it's a stubborn Android engineering politics thing. I can't even begin to explain how this happened, but, tl;dr: that 4th color was a huge problem to everyone involved. But, once it became a Big Thing, engineer middle managers...sigh. Not worth trying to explain. The amount of chicanery was really astonishing, odds are I'll never work at a BigCo again. Now, they're stuck with it, even though VPs were insisting it to be fixed since day -100. To all of your points , it sure looks like he's imitating the same logic to get that off-white...but then isn't using the important part: gotta use my/Google's color space. That's the magic to get contrast without even having to see the colors or measure ratios or any of that BS. (tl;dr: HCT color space, it's CAM16 strapped to Lab* L, and then you can describe contrasting colors by a delta in tone / L)