Hi everyone.
As per @Francesca and @Kenneth_Moreland , we are going to tweek the Fast map slightly. This change will be in 5.12.0-RC2. We are adding two more control points, which helps smooth the transitional center, and adds nicer colors 1/4 and 3/4 down the map, at least to my eye. As per analysis tools, this map has better discriminatory power. This map also appears to have more discriminatory power for color blind folks (tested visually by me using the color-blindness.com color blind simulator, not by analysis tools).
Here is a comparison of the old and new Fast color maps:
Finally, here is the git feature request to update the map: https://gitlab.kitware.com/paraview/paraview/-/issues/22392
As a side issue, we really need a better way to manage movement of control points for all maps that have numerous control points, including our new default. @Kenneth_Moreland suggested making this a feature of the color map editor. It is written up here: https://gitlab.kitware.com/paraview/paraview/-/issues/22379.
Alan