Quote Originally Posted by Danny
The whole point to the question was that I didn't want to get caught wearing some apparently ridiculous shade of butternut Reb gear. (I'm reminded of the ridiculous shades of "sky blue" Federal-issue pants reproductions I've seen).
The difference is that most dyes back then very natural or vegetable. Curt's post lays out the variations. The Federals tended to have "better" production facilities. Indigo, while a natural ingredient, does not have the same unstable properties as Sumac or other vegetable-based dyes. Hence Federal uniforms often look the same as they did 150 years ago (other than wear).

As has been stated, purchase a good garment from an authentic accurate sutler, wear it in the field, and within a season you will look fine. My RD II jacket, for example, from Becky Nall's Cotton City Tailors continues to evolve
in color, yet always looks "right."