The disc is drawn at full brightness, so a point's position is hue + saturation only — two colours that differ just in lightness sit on the same spot (the markers are drawn in their true colour, and the bar shows brightness). Lines connect your colour to the nearest Pantone, rebuilt NCS and nearest RAL so you can see the direction and size of each gap. RGB and CMYK markers coincide here because, with no ICC profile, the screen render is identical.