In Germany during World War II, many military uniforms were gray-blue. Why?

Gray-blue is the uniform color of the German Air Force, and the Army is gray-green, that is, German gray. German camouflage uniforms were first studied and put into use by the Waffen-SS before the war. To be clear, German uniforms use many colors. African troops are khaki, while the tropical clothes of air force airborne troops are dark brown. Starting from 1943, the new German uniforms are all dark brown and green. As for whether Germans attach importance to street fighting, I don't think so, because the level of street fighting in Germany really sucks. In addition to being more experienced than Britain and the United States, almost all the major urban wars on the eastern front of World War II were defeated by the Soviet Union, and even the early battles of Sevastopol and Brest were badly fought, and it took a lot of effort to win.