At long last here is the thread that I've been planning with respect to USAAF shirts from WWII. The thread will contain both original examples and reproductions with my comments.
From the 1943-44 Officer's Guide (Reprinted in Silver Wings, Pinks, and Greens):
Shirt, Service. The service shirt is of woolen or cotton material. Woolen materials are plain or twill weave worsted shirting, 10-1/2 ounces in each case. Cotton materials are broadcloth, cotton, olive drab or khaki, and poplin, cotton, olive drab or khaki. The weights of the cotton materials do not appear to be prescribed.
Authorized colors of the wool shirt are: Olive drab shade No. 51 (dark shade); drab shade No. 54 (light shade); khaki shade No. 1; olive drab shade No. 50. The cotton fabrics are khaki shade No. 1.
It is noteworthy that the regulations now current  authorize the wearing of the gray (drab [pink]) shirt which matches the drab [pink] trousers.
Either the olive-drab or the khaki shirt may be worn when the service coat is worn. Commanding officers may authorize the wearing of the olive drab or khaki shirt without the coat.
Here's a quick and dirty color translation:
No. 01 = Khaki
No. 50 = Yellowish green or "mustard"
No. 51 = Dark brownish green or "chocolate"
No. 54 = Grayish taupe/khaki that appears "pink" in certain conditions
The following photos are items that are in my collection.
Khaki No. 1.
Elbeco Officer's Regulation 2x2 Tropical (Washable Wool):
This is my favorite shirt and was purchased in 2005 as NOS from an eBay seller in Georgia. He is liquidating NOS from a store that supplied officers during WWII and I have purchased shirts, trousers, ties, USAAF belt buckles, and socks from him. All are NOS. The shirt is a very comfortable 17.5 x 35. (Still kickin' myself for just buying one and not two!)
A close-up of the same shirt:
V-Command U.S. Officers Regulation (Wool, Dry Clean Only):
This shirt was purchased as NOS from the same vendor in Georgia a couple of months later. Although the size is 17 x 35, this shirt is significantly more form fitting than the Elbeco shirt. (Note the Elbeco shirt in the background for color comparison.)
In 2005 I was able to purchase a number of uniform pieces from the estate of a 1945 West Point graduate (three time all American football player) in the unheard of size (mine) of 46L, with pant waist sizes in both 40 and 42. Included with the summer (Khaki No. 1) uniform were THREE broadcloth cotton shirts, all still pinned and in the original plastic packaging. Unfortunately, the shirts are 16.5 x 35 and thus too tight for me. However, I am keeping one of the shirts -- the "Bendone" that matches the summer uniform (lower right in photo):
Here is a series of photos with the shirts inside the Khaki summer uniform. First, the cotton broadcloth:
Next, the V-Command:
Finally, the Elbeco Tropical Worsted:
[Photo to Come]
Here, the Elbeco and V-Command shirts shown inside an original Hart Shaffner & Marx "chocolate" (olive-drab shade No. 51) winter tunic: