Preferences ...
from the Edit menu:
This brings up the ROI Preferences dialog:

Press the
button to
set the ROI colours for this session only. Changes will not be
saved to your user preferences if you only press the
button.
To revert to the default setting press the
button. To save the settings to your
user preferences so that they will always be set when you start
Jim, press the
button.
Click the
button when
you have finished setting your ROI preferences.