The Contrast Rule, Spelled Out
No white shirt on a white background.
Belize requires a white background and then adds something almost nobody else writes down: there must be contrast between the image and the background, with the example given as no white shirt on a white background.
That single clause resolves a contradiction people hit constantly. Countries demand a white background and neutral clothing, and a light shirt against a white wall leaves the shoulders dissolving into the backdrop — which is exactly what a face-detection system cannot segment.
Jamaica solves the same problem from the other end by varying the background colour to suit the applicant. Belize keeps the background fixed and tells you to change your shirt. Both are aiming at the same outcome.
Lighting must be uniform with no shadows or reflections on the face or in the background.