All of the military services imposes grooming principles on their military personnel, as part of their Dress & Appearance or Uniform regulations. For the US Army, grooming principles are controlled in Army Regulation 670-1 – WEAR AND APPEARANCE OF ARMY UNIFORMS AND INSIGNIA and are shown below:
General Grooming Principles
The Army is a uniformed service where discipline is umpired, partly, by the manner in which a soldier wears a prearranged uniform, as well as by the individual’s personal presence.
So, a neat and well-groomed presence by all soldiers is essential to the Army and contributes to building the pride and esprit essential to an operative military force. A vital constituent of the Army’s strength and military effectiveness is the pride and self-discipline that American soldiers bring to their service through a traditional military image. It is the responsibility of commanders to certify that military personnel under their command present a neat and military presence. Hence, in the absence of specific trials or guidelines, commanders must determine a soldier’s compliance with principles in this regulation. Soldiers must take pride in their attendance at all times, in or out of uniform, on and off duty.
The prerequisite for hair grooming criteria is necessary to maintain uniformity within a military residents. Many hairstyles are tolerable, as long as they are neat and conventional.
It is not probable to address every tolerable hairstyle, or what constitutes unusual or conservative grooming. Therefore, it is the responsibility of commanders at all levels to exercise good judgment in the administration of Army policy. All soldiers will obey with the hair, fingernail, and grooming policies while in any military uniform or while in neutral clothes on duty.
Leaders will justify the appropriateness of a particular hairstyle by the appearance of headdress when worn. Soldiers will wear headgear as described in the appropriate chapters of this guideline. Headgear will fit snugly and comfortably, without alteration or unnecessary gaps. Hairstyles that do not allow soldiers to wear the headgear accurately, or that interfere with the proper wear of the protective mask or other protective equipment, are forbidden.
Extreme, weird, or trendy haircuts or hairstyles are not legal. If soldiers use colors, tints, or bleaches, they must choose those that result in natural hair colors. Colors that take away from a professional military appearance are prohibited. So, soldiers should avoid using colors that result in an extreme presence. Applied hair colors that are forbidden include, but are not limited to, purple, blue, green, orange, bright (fire-engine) red, and glowing or neon colors. It is the responsibility of commanders to use good sense in determining if used colors are satisfactory, based upon the overall effect on soldiers’ presence.
Soldiers who have a quality of hair that does not part certainly may cut a part into the hair. The part will be one straight line, not partial or curved, and will descent in the area wherever the soldier would normally part the hair. Soldiers will not cut policies into their hair or scalp.
Soldiers may not wear hair-nets except they are required for health or safety reasons, or in the routine of duties (such as those of a cook). No further type of hair covering is allowed in lieu of the hair-net. The commander will provide the hair-net to the soldier at no cost.