Elven Characteristics

[Dulgakhôr]

Professor gives a bit about elven appearance in "Laws and Customs among the Eldar" (published in "Morgoth's ring (HoME 10)). In this he states that childrens of Men and Eldar seems alike in spirit (untainted by evil of the world and burden of memories), but...

This same watcher might indeed have wondered at the small limbs and stature of these children, judging their age by their skill in words and grace in motion. For at the end of the third year mortal children began to outstrip the Elves, hastening on to a full stature while the Elves lingered in the first spring of childhood. Children of Men might reach their full height while Eldar of the same age were still in body like to mortals of no more than seven years.

I guess you can fish out few more such pieces in Tolkien notes, but its extremely unlikely he left a more detailed description of physiology- it was simply not very important to him, and some fans found this frustrating:

"It seemed to men that Sauron was great, though they feared the light of his eyes. To many he appeared fair, to others terrible; but to some evil." (The Lost Road p. 67)
Thank you, Professor. And what did you say the color of his hair was?