The TeX syntax highlighter that I use colors all occurrences of a number followed by " in", e.g.
0 in or
32 in in a dangerous bright red, in almost all contexts. Why?
I don't know about Vim and its TeX/LaTeX syntax parser. It probably uses some rule that interprets a number followed by one of the keywords
My flavor of Emacs+AUCTeX (Aquamacs) doesn't do this: it highlights lengths only in the argument of