Anas (Radiallahu Anhu) reports:
"Rasullullah (Sallallahu alaihe wasallam) was neither tall nor was he short (like a dwarf... He was of medium stature). In complexion, he was neither very white like lime, nor very dark, nor brown which results in darkness (he was illuminant, more luminous than even the full-moon on the 14th night).The hair of Rasullullah (Sallallahu alaihe wasallam) was neither very straight nor very curly (but slightly wavy). When he attained the age of forty, Allah the Almighty granted him nubuwwah (prophethood).He lived for ten years in Makkah (commentary) and in Madina for ten years. At that time there were not more than twenty white hair on his mubarak (blessed) head and beard." (This will be described in detail in the chapter on white hair of Rasulullah (Sallallahu alaihe wasallam).
Arabic/English book reference: Book 1, Hadith 1