Many action expressions designate a note, either by name, by path, or by object designators such as parent or prevSibling.
An extension to the path mechanism allows you to replace the normal string literal used for note designation with an expression:
$Color(7*6) <-- the colour of the note named "42"
$Color($Path) <-- the colour of the note whose name is stored in the attribute "Path"
In the case of ambiguity, expression evaluation has the lowest precedence. For example, if a note happens to be named "7*6", the reference will be to that note, not to the note named "42".