Sahih Bukhari 3748:

Narrated Muhammad: Anas bin Malik said, “The head of Al-Husain(AS: علیہ سلام) was brought to ‘Ubaidullah bin Ziyad and was put in a tray, and then Ibn Ziyad started playing with a stick at the nose and mouth of Al-Husain’s head and saying something about his handsome features.” Anas then said (to him), “Al-Husain resembled the Prophet more than the others did.” Anas added, “His (i.e. Al-Husain’s) hair was dyed with Wasma (i.e. a kind of plant used as a dye).[Sahih Bukhari 3748]

Arabic Text:

حَدَّثَنِي مُحَمَّدُ بْنُ الْحُسَيْنِ بْنِ إِبْرَاهِيمَ، قَالَ حَدَّثَنِي حُسَيْنُ بْنُ مُحَمَّدٍ، حَدَّثَنَا جَرِيرٌ، عَنْ مُحَمَّدٍ، عَنْ أَنَسِ بْنِ مَالِكٍ ـ رضى الله عنه ـ أُتِيَ عُبَيْدُ اللَّهِ بْنُ زِيَادٍ بِرَأْسِ الْحُسَيْنِ ـ عَلَيْهِ السَّلاَمُ ـ فَجُعِلَ فِي طَسْتٍ، فَجَعَلَ يَنْكُتُ، وَقَالَ فِي حُسْنِهِ شَيْئًا‏.‏ فَقَالَ أَنَسٌ كَانَ أَشْبَهَهُمْ بِرَسُولِ اللَّهِ صلى الله عليه وسلم، وَكَانَ مَخْضُوبًا بِالْوَسْمَةِ‏.‏

Reference : Sahih al-Bukhari 3748
In-book reference : Book 62, Hadith 0
USC-MSA web (English) reference : Vol. 5, Book 57, Hadith 91