There is a high degree of formality within the military service, thus necessitating certain orthodox conduct, as well as adherence to a specific code of honor -- so meant then to instill respect by recruits to military authority, but also respect to one another, in addition to self-respect. Those that are part of the military are understood to know that they are part of the same team, with the same basic mission, and as part of that team, they are responsible for not only their given duties so assigned to them, but also to do right by their fellow soldiers, as well. Not too surprisingly, soldiers have uniforms so created not only as a form of identification but also as a form of team bonding, in the conscious recognition that they are together a band of brothers, united in the basic cause of resolutely defending their nation.
We live in a day and age, in which many a person is first judged by their outward appearance, and because of that, the military profession, recognizes the supreme importance of discipline, cleanliness, uniformity, respect, and obedience, as being part and parcel of what they so desire to see reflected from those that are its soldiers. That said, even though, soldiers may well be fighting to preserve freedom and democracy, the actual structure of their given military unit is never a democracy, for when an order from the commanding officer is given, it is expected to be obeyed without debate, and further to the point, each soldier knows their inherent responsibility to the other and thereby abides by it.
As much as individual liberty is celebrated, and as much as we know that we are sovereign as individuals; this philosophy for those that have on their soldier uniforms must always take a back seat to their duty to the state. That is a significant reason why, soldiers are indoctrinated into seeing themselves as being one part of a complete whole, and of which, each trained soldier is necessary for that whole to work correctly and efficiently. So, though soldiers come in all sizes, colors, and shapes, it is to be expected that once a soldier puts on the particular color of their uniform, that they will subsume their individuality to their military unit, at all times. This thus signifies why uniforms are one of the most important accouterments of what is required as a prerequisite in order to have an efficient and effective fighting force, and further to the point, why soldiers are trained to identify explicitly with the unit that they are an integral part of.
The fact that soldiers in a given unit wear the same uniform colors -- is most definitely a form of identification but also represents respect to those that are in authority, while also providing to those individuals a certain self-respect, for knowing that they are considered to be qualified to not only wear the colors of their unit, but to have as part of that deal, a band of brothers, to thus bond with. So then, in seeing all those others that have on the same uniform, each soldier knows that they are never alone, but instead are united together for the good of the cause, so entrusted to them.