The Blue Background Exception
White as standard, blue for white or sparse hair.
Colombia's Ministry of Foreign Affairs specifies a white background — except, in its own words, for people with white and/or sparse hair, in whose case the background must be blue.
The reasoning is practical rather than bureaucratic. Light hair against a white backdrop leaves no edge for a biometric system to find, so the outline of the head cannot be measured reliably. Switching to blue restores the contrast. Very few countries write this exception down, and if it applies to you, using white is a genuine rejection risk.