Hi Rick,
Very nice and useful script. What are the "canned magic hue parameters"? Magic settings, especially when they are used to mimic the behavior of other applications, isn't something we like too much in PixInsight. In my opinion, the Red, Green, etc. color buttons should set device/application-independent hue ranges by default, such as (just sample values, not intended to be these ones precisely):
Red = {330,0,30}
Green = {90,120,150}
...
and so on. Then you can create an auxiliary dialog to define custom color range presets. User-defined color range presets can be stored as plain text files (for example, CSV files) that your script can load very easily on demand. With this change your script would be a really powerful, general-purpose image processing tool. Let me know if you need help to implement this.