Gmail Notifier Menu Bar Icons
Designed to replace the default Gmail Notifier icons.
The original ones didn't go with the standard system menu bar icons at all, and these are designed to follow the standard OS X design cues: black when active (showing unread messages: this works very well with the Notifier's unread messages count numbers), grey/transparent when inactive (no mails to read), all of them slightly embossed as the system ones.
There's also a transparent red one for when there's an error (like no connection).
In the "Extra Icon" folder there is an "unread" icon in red, for those who prefer that to black when there's mail to read (that's the regular behavior of the original notifier menu bar icons).
To replace the original icons, right-click the Gmail Notifier application icon, select "Show Package Contents" and navigate to Contents>Resources. Copy the icons to the "Resources" folder, and accept when prompted to substitute the original ones.
Gmail Notifier Menu Bar Icons package also contains the original icons in the "Original Icons Backup" folder, just to keep you safe.