What background colour must the visa photo have?
A white background, with the full face visible.
In detail
The document states it in a single line: “colour photograph (2X2) depicting full face with white background” — colour, white background, full face visible. All three conditions must hold together.
“Full face” means no part of the face is obscured. Hair, a cap or a head covering must not cross the outline of the face. The document says nothing specific about glasses, but if reflections hide the eyes it is hard to argue the full face is visible.
The background must be white — photos taken against a light grey or bluish wall are a common cause of rejection. Stand in front of a white wall or white sheet, and watch that your shadow does not fall on the background.