see:
http://www.flickr.com/photos/opto/6230424431/in/photostream/

but… there is no layer created.
saving and reopening file: the new layer appears.

deleting the layer:
Traceback (most recent call last):
File “/Applications/Typotools/RoboFont/RoboFont.app/Contents/Resources/lib/python2.7/vanilla/dialogs.py”, line 49, in alertDidEnd_returnCode_contextInfo_
self._resultCallback(self._value)
File “lib/UI/inspector/__init__.pyc”, line 1344, in _delLayer
File “lib/fontObjects/doodleFont.pyc”, line 183, in removeLayer
File “/Applications/Typotools/RoboFont/RoboFont.app/Contents/Resources/lib/python2.7/defcon/tools/notifications.py”, line 125, in postNotification
callback = getattr(observer, methodName)
AttributeError: ‘NoneType’ object has no attribute ‘action’
Traceback (most recent call last):
File “lib/doodleDelegate.pyc”, line 65, in sendEvent_
File “/Applications/Typotools/RoboFont/RoboFont.app/Contents/Resources/lib/python2.7/vanilla/dialogs.py”, line 49, in alertDidEnd_returnCode_contextInfo_
self._resultCallback(self._value)
File “lib/UI/inspector/__init__.pyc”, line 1344, in _delLayer
File “lib/fontObjects/doodleFont.pyc”, line 183, in removeLayer
File “/Applications/Typotools/RoboFont/RoboFont.app/Contents/Resources/lib/python2.7/defcon/tools/notifications.py”, line 125, in postNotification
callback = getattr(observer, methodName)
AttributeError: ‘NoneType’ object has no attribute ‘action’

and the layer is not deleted, but its color is changed! :)