It was narrated from Jabir that: On the Day of the Conquest of Makkah, the Messenger of Allah SAW entered (the city) wearing a black turban, and he was not in Ihram.
The Prophet ﷺ also chose to wear a black turban which was symbolic of his humility and modesty despite his great victory. He wanted to remind himself that no matter how much success he achieved in this life; he was still only human and must remain humble before Allah SWT. This is an important reminder for us today as well; no matter how successful or powerful we become in this life; we must always remember our place before Allah SWT and remain humble before Him at all times.