The reg's here.
30-10. Wear of uniforms by U.S. civilians
a. Authorized U.S. civilian personnel attached to, or authorized to accompany forces of the United States, including DA civilians, are authorized to wear utility uniforms only when required in the performance of their duties, and when authorized by the MACOM commander. The procedures for purchasing uniforms, footwear, and insignia are contained in AR 700-84, chapter 3 . Only the insignia described below is authorized for wear on these uniforms.
b. Insignia for civilians.
(1) Description. The woodland subdued insignia is a black equilateral triangle, 1¼ inches long per side, with the letters "U.S." in olive-drab color, ¼ inch wide and ½ inch high. The triangle is printed on an olive-green colored cloth background, 3 inches long and 2-½ inches wide. If applicable, the insignia also indicates the designated assignment in black letters, ¼ inch high. The desert subdued insignia is the same size, with khaki or tan letters on a black cloth triangle. The triangle is printed on a khaki or tan cloth background.
(2) The authorized designations are as follows.
(a) Scientific consultant.
(b) Operations analyst.
(c) War correspondent.
(d) Technical observer.
(e) Ordnance technician.
(h) Logistics specialist.
(j) Ammunition surveillance.
(3) Insignia for civilians performing duties not listed above, or when specific designations are not required, will conform to previously described insignia, except the insignia will not denote duty assignment (see fig 30-2 ).