|Munsell color coordinates are converted to xyz in: G. Wyszecki, W. S. Stiles. 2000. Color Science: Concepts and Methods, Quantitative Data and Formulae, 2nd Edition. We have converted xyz to Luv color coordinates according to standard formulae.
A good colored diamond should have both high brightness and saturation. On the Brightness/Saturation diagram of the fixed yellow hue one can see yellow colors of different brightness and saturation. These colors are tending to be near the upper right corner.
The Munsell color chips positions are placed as described before.
While grading diamond fancy color a grader determines the masterstone or color chip closest to the graded diamond. For color calculations it is necessary to draw borderlines between different color grades. First we draw these borderlines in the middle between Munsell color positions.
Then we found that sometimes these borderlines have a little logic and we have changed borderlines positions in a way that better describes the logic of color difference. It is just an idea how the current color grading system can be improved in future.
For different diamond spectra shown before, here there are coordinates of the diamond plates of various thickness having same spectra are plotted on the diagram. Here a question comes: at that thickness the given material will receive a fancy grade?
The middle blue line shows that this material can be fancy colored in very thin plates. The red curve shows bigger range between max and min thickness.
From the one hand, maximum and minimum thickness corresponds with the particular color grade. From the other hand, its corresponds with light path in a cut diamond