@PotomacBobI try to provide only (or at least mostly) the characteristics important to the story. So, in a particular story that I am writing, in the first paragraph the character mentions he is a "gentile" (non-Mormon), relevant because it is 1939 and he is in rural Utah, just a bit east of SLC, and most of the people in the community are members of the Church of LDS. It is mentioned he is a Ranch Hand too.
This is a factor (implied but not explicit) why he decides to join the US Army. I believe I am "showing not telling" why he is more tolerant of diverse people he encounters over the course of the story. He has been a discriminated minority (despite being a WASP male); he experiences further prejudice (if not quite discrimination) being a "Yankee" in the "Deep South" (South Carolina, Georgia); he witnesses fellow soldiers being discriminated against (Catholics, and "Yankees").
Much later in the story when he encounters the discrimination, even atrocities committed by the N@zis, there is a context in the story of the imperfections in the USA; although not nearly the scale of what is witnessed in 1944/45 Europe!
I have an extensive document detailing the appearance, ethnic background (important in the 1940's USA, and a source of jokes and friction among soldiers), their place of birth/where they grew up, and if different where they were before joining the Army, their education, job(s), etc. Not nearly all of it will make it into the story, but it does influence how their characters act. In particular those from urban areas, and those from rural areas.
So, most characters will be distinctive by their place of origin, and manner of speech; more so than their appearance. Albeit some individuals with a distinctive appearance will have it commented about, as you should expect from a bunch of young soldiers.
As you would expect in a group of people, some will be more prominent, and others less so. As the combat grinds on most of the replacements are barely detailed, if at all.