Tracers come in a rainbow of colors depending on nationality and purpose. During WWII, the Germans favored a gold (actually yellow) tracer. The WWII American M21 .50 BMG round had a brilliant white tracer which was visible by its target, and was commonly called a Headlight tracer. It was intended to terrorize German and Japanese fighter pilots. .38 Special red tracer ammo was issued to US naval flight crews for signaling purposes, and .38 Special tracer bullets in several other colors were under development near the end of the war, but were never made in any quantity or issued. I have read about infrared tracers visible only by using night vision goggles. I also remember reading about tracer bullets which aren’t actually tracers that burn but instead have discs of highly visible material on their bases which can be seen by the shooter. I don’t know anything more about those.
I was shooting my M1 carbine with hand loaded 90 gr short jacket soft point bullets with a rising sun behind me. I got a wonderful tracer effect with the sun illuminating the bright copper flat bases on the new bullets. I transitioned to some plates at 200 and 300 yards just to see it longer and enjoy the arc.
A range officer quickly showed up to stop the “tracer” firing, and I had to explain to him what was actually happening.