It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the standard (rayah) of the Messenger of Allah (peace and blessings be upon him) was black and his banner (liwa') was white.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الفيء والغنيمة / 13061