Armies can indicate the bodies defenses in action against an invading bacteria or virus. They can also indicate conflict either within or with others.
A subversive or underground army can indicate a serious threat to the body such as cancer.
Army uniforms indicate you have a regimented way of thinking that needs to change. In the army troops are trained through boot camp to not question the orders of their superior regardless of the threat to their own life. Green army uniforms ask you to listen to your heart rather than your head.