ISTR that there was some camo pattern (UCP?) where the dirtying of the pattern was used as an excuse as to why it wasn’t so effective when clean.
I think the problem is nobody wants to look like a REMF so everyone wears camo including those who are never going to be seen by an enemy soldier.
I think it was on Hardcore History that I heard the story of a journalist in Belgium in 1914. He had thought, like many, that the German’s feldgrau uniforms would make for poor camouflage, but they kicked up so much dust that they seemed to vanish. The same could not be said of the French uniforms of the time. They got over their fixation with red trousers and hats eventually, but blue–that picture is faded and the real color was a pale grayish-blue, lived on.
Well, of course camo is worn by those who will never be seen by an enemy soldier. That’s kind of the point, isn’t it? 
Has the military ever considered dressing soldiers exactly like the native population for urban warfare? I suppose friendly fire would become a risk then, but maybe they could mitigate that by wearing a particular type of boot or scarf. Seems like it’d be pretty effective camouflage against the enemy, at least.
Guerillas/terrorists commonly do this. Intelligence agents and special forces in some situations do. Conventional military forces seldom do, because it’s against the laws of war not to wear a uniform that identifies you as a combatant and is a great way to be summarily executed if you get caught. Also, you might rightfully get blamed if the enemy mistakes civilians for you and kills them.
Any boot or scarf that identifies you to friendlies would identify you to the enemy.
It would also contravene the laws of war.
ETA: Nijaed, of course.
Heh - my old field manual for urban combat dealt with the challenge presented by the different colors in built-up terrain by dryly stating that “after a minimum of time in an urban combat setting, the uniform will be covered in dust and grime that mimics the local environment” or words to that effect.
Still - one can do a bit with fit. We had 2 flecktarn uniforms issued - one for combat with loose-fitting pants with deep pockets and suspenders, and the jacket worn loose at the waist and hem. The one for garrison duty and travel came with fitted pants - same model jacket, but worn adjusted to show off one’s soldierly figure, with metal insignia instead of cloth ones, no bulging pockets, etc.
Kinda bizarre deciding what to include and not include in the laws of war. Nuking a major metropolitan area is fine and dandy, but dressing like the locals is right out!
Yes, because you can tell that the people nuking your cities are the enemy.
Can’t find a clip, but from the Good, the Bad, and the Ugly:
They come across a bunch of soldiers in gray uniforms.
Tuco: Hurrah! Hurrah for the Confederacy! HURRAH! Down with General Grant! Hurrah for General… What’s his name? Lee! LEE! Ha ha. God is with us because he hates the Yanks too. HURRAH!
The general wipes the dust off of his blue uniform…
Blondie: God is not on our side because he hates idiots also.
Correct me if I’m wrong, wasn’t that codified in the Fourth Geneva Convention? Which was 4 years after they dropped da bomb YVAN EHT NIOJ.
Or was something said earlier?