How about something which will allow you to change a priority-colour to a different one.
I'll explain, because it seems a bit unclear:
If you have drawn a priority screen, you test it and you see that you accidently placed the wrong priority to something on a drawing, you have to go through your history, delete the wrong colour and draw it again (or over the first time).
If it could be done by just changing that colour to another one, it wouldn't take that long.
There seems to be only one problem with this: If you just adjust the pallet, there's the possibility of a colour (for this example: green) given to one thing where it is correct and to another thing where it should be yellow.
You'll see what'll happen.
Is such a feature possible, or is it a bit over the head?
-Kon-Tiki-