Are Mahtan, Nerdanel, Maedhros, Amrod and Amras the only red-headed Elves?

Question

Are the they the only Elves or at least Noldor that bear red hair?

Answer 1

I don't think Tolkien ever stated that Nerdanel had red hair but rather it was assumed she did. But I believe you are right in that their family (and members of their kin) possessed red hair. There's probably a letter or script from Tolkien mentioning this but from the Lord of the Rings wiki atleast:

...they are the only attested examples of elves with red hair. Nerdanel's father Mahtan and three of her sons (Maedhros, Amrod, and Amras) are described by Tolkien as having red hair (actually a reddish brown) and this is described as a trait "of Nerdanel's kin". Nerdanel's own hair color is never specifically stated, although it is said that she possessed a ruddy complexion and so it is assumed that Tolkien did indeed intend Nerdanel to have red hair.

Answer 2

Apart from the Noldor, Vanyar, and other tribes that had a major role in the Silmarillion, there were an uncounted number of Elves living in Arda who we never learn anything about. Some of them might have had red hair.

http://tolkiengateway.net/wiki/Avari