IR is often used for facial recognition (invisible pattern projectors or to better illuminate skin texture). However in colour pictures you get a strong purple cast in some conditions, like bright sunlight, due to excess near infrared radiation. This is not desirable for photography, so most consumer cameras have IR cut filters for this reason. The filter looks like a transparent piece of glass or plastic, but it will shimmer red if you hold it at an angle. Not to be confused with the normal anti reflective coatings on lenses (these often look green/purple).

As the sibling says though, plenty of rear facing cameras are also IR sensitive. I imagine there's some onboard processing to correct the colour balance.

What kind of light does the FaceID system use? Or does it have a separate camera for the invisible lights?