AR 670-1 paragraph 3-7f (See extract below), outlines the requirements for wearing of backpacks. Perhaps most important in this paragraph is the phrase which states:
Bags (to include civilian gym bags, civilian backpacks, or other similar civilian bags) must be carried only in the hand if they do not meet the criteria outlined in paragraph 3–7f.
The next statement:
(2) If Soldiers choose to wear a shoulder bag while in uniform, the bag must be black or match the camouflage pattern uniform being worn, and may not have any commercial logos.
makes it clear that only Black or Matching Camouflage backpacks may be worn. However this does not prevent them from being carried in the hand.
“camouflage pattern uniform”
camouflage pattern is the adjective specifying which uniform and the subject is uniform. This implies they’re talking about the outfit (blouse, shirt, pants, and boots as you are required to have all in order to be in uniform) so coyote tan is authorized as it is a color in the uniform. Even if you don’t consider the boots as part of the uniform: they are matched to said uniform, which means anything in that color matches the uniform.