Sahih Bukhari Volume 7, Book 63, Hadith Number 225.

Narrated By Abu Huraira : A man came to the Prophet and said, “O Allah’s Apostle! A black child has been born for me.” The Prophet asked him, “Have you got camels?” The man said, “Yes.” The Prophet asked him, “What color are they?” The man replied, “Red.” The Prophet said, “Is there a grey one among them?’ The man replied, “Yes.” The Prophet said, “Whence comes that?” He said, “May be it is because of heredity.” The Prophet said, “May be your latest son has this color because of heredity.”