Tweetie for Mac has been released, a Twitter client with a simple, but still feature rich, user-interface.
Unfortunately the menubar icon uses a glowing blue icon to indicate new Twitter messages.

I’ve changed both icons to be greyscale and made them less heavy by making them an outline of the Tweetie dock icon. I’ve also added one pixel to their height to make it align better vertically.

Download the zip file containing both icon, copy them to
/Applications/Tweetie.app/Contents/Resourcesand restart Tweetie to use these icons yourself.
after i replaced them, the menu bar icon dispeared!
The icons work after you restart your computer (something about the system registering icons for the duration of a session). I like the greyscale–less distracting when you have other things to do. Thank you to Casper Kuijjer.