Dark or light? Until recently, it looked like a no brainer and I was advising everyone to use dark backgrounds. Now experience makes me modify that advice. It's not so simple after all and you'll have to make a judgement call.
It sounds unlikely, doesn't it? Most speech readers enter into a beautiful relationship with the speech notes and treat the audience as if it doesn't exist. But here's an amazingly simple device for keeping you and your audience together - even when every word is pre-written.