Sayyiduna Abu Wahb (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) said: "Hold fast to the reddish-yellow (ashqar) horse with a white blaze and white legs, or a dark red (kumayt) one with a white blaze." Muhammad (bin Muhajir) says: I asked him: Why did he give preference to the ashqar? He said: The Prophet (peace and blessings be upon him) had sent out an expedition, and the first person who came with (news of) the victory was the rider of an ashqar horse.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الفيء والغنيمة / 12898