It is optional.
You just have to navigate to the skin's folder (C:\Program Files\J River\Media Center 12\MegaSkins\Noire), open up the main.xml file in notepad, scroll down to the <MENU> section, and edit the "<Data Alpha="230" />" tag to say (I believe) "<Data Alpha="255" />".
Then it's just a simple matter of saving the main.xml file, and either closing and restarting MC, or choosing a different skin, and choosing Noire again.
You may also want to rename the Noire folder to something else so that the next time you install a new build of MC, it doesn't overwrite the skin, or you'll have to do all of this again.
Oh, if only there were a tool... built in to MC, ideally, that could make such changes like this on the fly... you know... something that could change the Effects on Skins without having to manually edit an xml file...