At a minimum, you should wear blush on your cheeks. That will help somewhat with defining your face a bit more under the bright spotlights. That being said, it won't be enough: you'll need to do more definition. Just the blush will be a stripe of color in a sea of same color.
Contouring involves using shadowing and highlighting to essentially redraw your face. And, yes, you can modify your features that way. If you've ever seen drag queens, they will modify their jaw line and make it less square (so less manly) by shadowing it.
At a high level,
- for shadowing, you'll want to use a dark color (browns or bronzers work well for this) and apply it under your cheekbones, along the sides of your nose, under your jaw line. Essentially, you're putting shadows where shadows would normally be on your face.
- for highlighting, you'll want to use a pale color, generally a bit shimmery (it can be a beige or a mellow white) to highlight above the eyebrows, on top of your nose, the top of the cheekbones, maybe even the tip of your chin. Essentially, wherever you catch a sunburn, that's what you would highlight.
Doing all of this will help you look less like one color overall and get back to a normal 3D look. Now, it's especially important if you will be under bright spotlights and if you will get your picture professionally taken. If it's a performance setting without bright spotlights, you won't need to do this nearly as much but, with the distance between you and the audience, your face will look a little flatter so it's not bad to do it... you just would contour it a bit less since people would see you from closer.