You plot the visible gammut of your favourite color space (RGB, CIE LUV, CIE LAB, preferably one that is perceptually uniform) in 3D space. You get either a cub

You plot the visible gammut of your favourite color space (RGB, CIE LUV, CIE LAB, preferably one that is perceptually uniform) in 3D space. You get either a cube (RGB) or something that resembles a skewed cube (CIE LUV/LAB). Then take the corners which are farthest apart and place a line between them, or place a line between any other two points which are sufficiently apart from each other. You sample however many points you need along that line and that is your color scale. Now one variation is instead of a straight line, you draw a spiral along it. And you got yourself a CUBEHELIX color scale (https://www.mrao.cam.ac.uk/~dag/CUBEHELIX/ https://www.mrao.cam.ac.uk/~dag/CUBEHELIX/). Though CUBEHLELIX works inside a RGB cube and not a CIE LUV/LAB mesh, but the principle could be applied to other color spaces, too. One thing to watch out for when working with these non-linear color spaces which have a weird shape in 3D space is how to deal with colors outside of the gammut. Simple clamping only works in RGB, in CIE LUV/LAB it's not that simple, because for any given L the range of UV/AB varies. And often times clamping is not the most (perceptually-)accurate solution.