The point is that quantizing the range makes it easier for humans to choose colors. But there's already the #ABC hex format, which while less intuitive to non-techies has the huge advantage of being well-established.

But it doesn't make it easier for humans to choose colors. For a specific list of detent colors, it reduces the amount you have to memorize relative to full RGB. But to actually reason about colors, you want a non-arbitrary scale; HSV (for instance) gives you hue direction and then you can slide saturation and brightness around.