Roger Hunt's Colonels in Blue series

Beginning with the 1990 publication by Olde Soldier Books of Brevet Brigadier Generals in Blue (Rev-1997) co-authored with Jack Brown, Roger Hunt has built quite a reference book legacy in his name. Sometime this year (at least according to the most current schedule), McFarland will publish Colonels in Blue — U.S. Colored Troops, U.S. Armed Forces, Staff Officers and Military Units, yet another volume in his long-running series that aims to exhaustively compile photographic images and information on all officers who "attained the rank of colonel in the Union army, but failed to win promotion to brigadier general or brevet brigadier general." Publication has followed a winding course through three different outfits (see the summary below), and the series now seems to be finally nearing its end after two decades.

Other Colonels in Blue - A Civil War Biographical Dictionary series volumes from McFarland:
• Colonels in Blue - Missouri and the Western States and Territories (2019).
• Colonels in Blue - Illinois, Iowa, Minnesota and Wisconsin (2017).
• Colonels in Blue - Indiana, Kentucky and Tennessee (2014).
• Colonels in Blue - Michigan, Ohio and West Virginia (2011).

Colonels In Blue - Union Army Colonels of the Civil War series volume from Stackpole:
• Colonels In Blue: The Mid-Atlantic States - Pennsylvania, New Jersey, Maryland, Delaware, and The District of Columbia (2007).

Colonels In Blue - Union Army Colonels of the Civil War series volumes from Schiffer:
• Colonels in Blue: New York (2003).
• Colonels in Blue: The New England States - Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, Vermont (2001).

So what's left to do before this mammoth project is finally concluded? In the area of units formed by southern Unionists, Hunt has already addressed Tennessee and West(ern) Virginia, but, as you know, most Confederate states fielded Union regiments. Since there isn't enough of those to fill a standalone volume of similar size to the others, I can imagine those officers might be included in the upcoming 2021 volume's broad-sounding "U.S. Armed Forces" section. We shall see.