Your photo shoot with the stage production is done, but just for future reference, I will post my answer here.
I hope you indicated whether using film or digital. Anyway, I am a stage actress, and have a long history of stage productions starting since I was 12 and am practicing professionally now. I was also a major in photography and am pursuing fine art photography.
For film, it is best to use high speed film, if possible, get higher than 400 or push your film. Using flash for dramatically-lit productions may wash out the intent of the lighting designer and may distract the actors/performers, unless it is a press night (meaning, a night for press photographers, writers, critics, and therefore, flashes are expected). Keep a tripod in hand and telephoto lenses. Make sure you are posted at a good distance without distracting other viewers. Be there before the show starts so you can do your tests, meters, or if using digital, your white balancing, if preferred. Keep your shutter speed at 1/60 at the lowest because there's usually a lot of movement on stage, unless there is a monologue. Remember not to use flash unless it is a press night. In fact, some productions don't allow cameras in the venue unless it is a press night, or unless you are the official photographer. If I'm not on stage and if I take photos of productions, I make sure I get the drama of the lights and the emotions/energy of the performers. I use Kodak Gold for color for candid shoots because of the vibrance of its colors. I even use it for stage productions. Just make compensations for the speed of the film.
I know of other experimental lighting support, like a hand-held flash (if it is a press night), and setting the camera at aperture priority set at smaller apertures for maximum depth of field/focus, so the shutter speed is longer. With the hand-held flash properly metered, a still moment will be captured, but since the shutter speed is low, there will be motion blurs and lighting plays, which could be nice.