Gregs analysis is correct, this is the problem of the AppKit not storing the typing attributes for NSTextView. Asusual with encoding stuff, any change here wont be backwards compatible. That's why I would like to have an agreed on solution, so we only need to change it once.

I would suggest to store all the typing, selection and mark attributes in a way similar to the onces used for keyed encoding by Apple, that is in the special class NSTextViewSharedData, which is already in the file NSTextView.m.
This does not necessarily mean that we have to use this class during text processing as well. We can decide on that later on. I must admit that the current mechanism to synchronize different text views, although it is very elegant, looks rather complex to me.

1) New Applciation
2) Add a TextView
3) Change the TextColor
4) Save the document
5) quit the document
6) Open The document again
7) select the textView
8) The textView textColor is black ( default )

The strange thing is that ok: in GormTextViewAttributesInspector
is called with sender textColor when the document is closed ( that odd )
TODO : check other Inspectors too