How Much Do the Minute Details Count?

While editing my book recently, I found that I needed a line translated into Latin. The thing is that I spent quite a lot of time trying to get a translation. But the thing is that even though it is a pretty small detail, I spent a whole lot of energy trying to get it right.

Just how much do the really small things count? I mean, the big things like plot, dialogue, and characters are definitely important, but what do you guys think about getting small things like a character's hair color right throughout the book? I'd like to hear.