Experimental color picker which finds a gradient through the CIE XYZ color space which runs along the edge of a circle centered on a copunctal point and intersecting with a user selected color. The top half of the gradient is drawn as it would appear to a person with the color deficiency corresponding to the selected copunctal point.
There are two straight white lines drawn over the color space. One is drawn from the copunctal point through the user selected color. The other line represents the major axis of the selected color deficiency. This axis is what color appears to collapse on for someone with that deficiency.
The ring of dots represent the 15 colors from the D-15 color test. Notice how the order of the colors in the loop would be lost once they collapse to the axis.
Copunctal point positions taken from this page.