During WW2 the tracers were red or yellow for Soviets, Americans, and British. For Germany it was Green, blue, or white. Japan used Purple, blue, and white tracers
P.S. Bullets were already tracer

Modern day tracer colors for countries of all NATO forces are Red so the countries are Belgium, Canada, Denmark, France, Iceland, Italy, Luxembourg, the Netherlands, Norway, Portugal, the United Kingdom and the United States. The other member countries are: Greece and Turkey (1952), Germany (1955), Spain (1982), the Czech Republic, Hungary and Poland (1999), Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia and Slovenia (2004), Albania and Croatia (2009), and Montenegro (2017). While Russia and China uses green tracers