Celebrate the centennial during the Mt. Lebanon Tennis Center’s Throwback Days, through October 22. If you show up at the center ready to play properly attired in sparkling tennis whites, instead of the scandalous blues and blacks and pinks and heaven knows what-all, OR if you show up with a sensible wooden racket instead of these show-offey metal and fiberglass things, you will be rewarded with a set of properly colored white tennis balls, for your enjoyment. Head tennis pro Hank Hughes says the center even has a few of the wooden rackets to lend out.  He asks that you return the balls when you are done playing, so the center can use them for practice.