What is the difference between infrared and no-glow flashes?

An infrared flash is going to produce a black and white picture and will be visible in the dark. It produces a dull red glow that is not bright enough to catch your attention in the dark but if you looked right at it, it would be visible. A No-Glow flash is going to produce a black and white picture and will NOT be visible in the dark. It produces no visible light unless you are very close to the camera and will be nearly invisible in the dark.