(Mac, Version 8 (8.6.24101.05002, 2024-04-10))
Assigning Color to an Layer gives another Color-Dialog then assigning Color for _curvatureGraph.
Layer Colors can be assigned by click on the color While and press Enter. (much nicer)
_curvatureGraph Colors need a color drag&drog from the Color-Dialog to the Target-Tile. (not very flowy)