You can change palettes with GIMP. It doesn't have the preview feature you described and isn't the best UI by far tho.
Gimp: Colors->Map->Set colourmap to change the colourmap.
Sorting the colourmap before by hue ("Rearange Colourmap"->right click->sort by hue) might help to make it a bit easier.
Your current palette contains the string "(imported)". Duplicate that one, change colors like you want, and close the dialog.
There are probably a bunch of other editors which can do that but i could throw together something like you described in a bit in python if there is any interest. (Need to check which GUI toolkit to use before tho).
You can change palettes with GIMP. It doesn't have the preview feature you described and isn't the best UI by far tho.
Gimp: Colors->Map->Set colourmap to change the colourmap.
Sorting the colourmap before by hue ("Rearange Colourmap"->right click->sort by hue) might help to make it a bit easier.
Your current palette contains the string "(imported)". Duplicate that one, change colors like you want, and close the dialog.
There are probably a bunch of other editors which can do that but i could throw together something like you described in a bit in python if there is any interest. (Need to check which GUI toolkit to use before tho).