These are the TIFF files for the Dials for Contrast DCP experiment – there are 4 sets of colors, R,G,B, and white (but white so dim in luminance that it is deep grey).
Each set has a dial that starts at 6%, 4.5%, 3%, and 1.5% and which gradiently go down in a radial to 0%? There is also a TIFF with a ring of tic marks and numbers that can be used to measure where the color can no longer be seen.
Would some secondary colors be interesting?
As always Mr. Phelps, these are 16 bit, 2020 files. Adjust your DCP Creation tool accordingly.