Aggregate labels for collapsed mail thread

[helmo]

In the Thunderbird desktop client the parent of a collapsed mail thread gets the highest color label from it's following mails.

This way the label is still visible even when a thread is collapsed.

It would be nice if this plugin can also have that behavior.

With the UI style 'thunderbird' it uses the font-color, which naturally only show one color ( and blending colors would probably be confusing ;) )

With the 'bullets' and 'badges' styles it might be possible to just show all labels that are present in the thread.