Donning specific colours on every single day of Navratri is a standard custom, as each colour represents a different high quality of your Goddess. महानवमी, (नौवां दिन) शरद नवरात्र व्रत पारण Night time can be thought of an element of Mother Divine as it really is night that provides solace, https://www.youtube.com/watch?v=QIX0JZlLsgE