What is the significance or symbol in the uniforms of both the Nazis and the prisoners in the book?

The Nazi's clean-cut, black uniforms represent authority, power, and an oppressive force to the Jewish prisoners at Auschwitz. The swastikas on the Nazi soldiers' armbands represents the Third Reich and their loyalty to Adolf Hitler. The color black also symbolically represents the evil, wicked deeds of the Nazi regime, such as the systematic annihilation of the European Jewish population. The Nazi uniforms stand in stark contrast to the worn, dirty uniforms that resemble striped pajamas that the Jewish prisoners are forced to wear.
The prisoners' uniforms do not fit properly and are reused by other prisoners when someone dies. The prisoners' uniforms symbolically represent their oppression and servitude. The stripes on their uniforms also relate to prison bars and represent their seclusion in the violent, harsh concentration camps. The fact that the prison uniforms resemble pajamas symbolically represents Bruno's naive, innocent perspective. He does not understand that the people inside the fence are prisoners and suffer under the horrific conditions of their environment. Overall, the uniforms are symbols of separation, reflect the balance of power at Auschwitz, and represent the Nazi authority and Jewish servitude in the concentration camp.

There are two distinct "uniforms" in The Boy in the Striped Pajamas. The Nazi officers wear official Officers uniforms to signify authority and power; these uniforms symbolize control and higher status over the prisoners. The prisoners in the camp wear striped grey clothes (which Bruno mistakes for pajamas on Shmuel). These clothesstrip the prisoners of their identities and ensure they conform to their lower status in the camp.
The striped "pajamas" are significant because they represent the branding that occurred on a larger scale in Europe (Jews were forced to wear yellow Stars of David; Nazi supporters wore red armbands with black swastikas to show allegiance to Hitler's cause).The pajamas may also represent Bruno's childish innocence (or naivety) about the outside world. When he puts on the "smelly" old, grey pajamas to sneak into the concentration camp with Shmuel, he is mistakenly killed alongside his Jewish friend. This shows readers the true horrors of artificial branding; even the Commandant's own son can be killed if he innocently ignores the division established by the uniforms.