Captives in Blue: The Civil War Prisons of the Confederacy. By Roger Pickenpaugh.  (2013.  Pp. 320.  $49.95.  Hardcover. Lexington: University of Alabama Press.  Tuscaloosa, AL 35487-0380. http://www.uapress.ua.edu/) ISBN: 978-0817317836. A follow-up to Pickenpaugh’s earlier publication, Captives in Gray: The Civil War Prisons of the Union (2008), this book uses soldier diaries, newspaper …