Isn't this just RGB, with 246 of the 256 values removed from each channel?
My other question here is, are "R", "G", and "B" channels the best way to reason about color? Isn't HSV more intuitive?
Despite my background in color science, I find RGB more intuitive. With HSV I have to remember the chirality of hue and it's zero point, and when changing hue I find it difficult to reason about saturation. In practice this means I must "nudge and judge" with both systems. With RGB I can always make progress. With HSV I guess hue wrong about half the time. I could probably improve this.
To be fair, I'm also colorblind. That's probably relevant.
Anyway, I'd say the answer to both your questions is: "sometimes"