Hello,

Firstly please don't waste any money on a new lig, they make little to no difference. They certainly won't make your sound noticeably darker or brighter. The big onions when it comes to sound is your mouthpiece. The modern link STM tend to be quite stuffy and ive found a lot where the rails are not straight or the tip rail is un even. They do make great blanks for a refacer to work on. IF you get a good refacer in your area to work on the piece you can get it to be a real balanced centered sound, then work on getting a bright or dark tone with reed choice and  embouchure.   

Like previously mentioned, don't worry about a ligature.  Mouthpiece will make a bigger difference in the sound.  I've never known of anyone to make changes on their set-up during a gig, but if you want to try a slightly brighter sound perhaps experiment making a small baffle in your mouthpiece with something temporary such as dental wax.  It's a lot cheaper than forking out for a new expensive ligature or mouthpiece with the possibility of not liking it! :)

You could also try some of the other Vandoren reeds.  The Vandoren green Java’s tend to play on the brighter side at least in comparison to the ZZ and V16.   

If you have the opportunity to try some ligatures before you buy them I would definitely do so. The fashion in which a ligature makes contact with the mouthpiece and the reed effects the way the reed and mouthpiece vibrate. Rovner leather ligatures tend to dampen the overall sound of the reed and mouthpiece (this also varies depending on the ligatures model).  The FL ultimate ligature and a few of the other metal ligatures on the market will probably open the sound of the mouthpiece up a bit.  But try them in person if possible; what works for one person does not always work for everyone.  

Hi, i read a long time ago in "Chasin the Trane"(Da capo press) this story about Dewey Redman passing by at Trane`s house because he was having trouble finding "the right mouthpice". Well, Trane`s  quick answer was  an airline bag full of mouthpices and the sentence "pick anything you want".
I suggest you to visit David Liebman`s website and read this fine article about mouthpieces and reeds and everything.Best wishes!
 http://www.daveliebman.com/Feature_Articles/nirvana.htm