Actually, there is more evidence for red hair including his essay in the
_Hannibal Daily Journal_ in 1853 "Oh, She Has Red Hair."
Also this passage:

I was born red-headed--maybe that accounts for my passion for the gorgeous
and ornamental.
- quoted in _Abroad with Mark Twain and Eugene Field_ (Fisher, 1922).

Both online at:
http://www.twainquotes.com/Redheads.html

As to height, I again refer to both the 1867 and 1891 passport applications
where he wrote 5'8" on both.

As an aside, the 1867 passport eye color entry looks like the word "dark"
before gray is struck out.

Barb