The United Kingdom was the first to develop and introduce a tracer round, a version of the .303 cartridge in 1915.[2] The United States introduced a .30-06 tracer in 1917.[3] Prior to adopting red (and later, other color) bullet tips for tracers, American tracers were identified by blackened cartridge cases.
Da wikipedia
1915. Spero sappiate l'uso del 303 e del 30.06
Edit. Another use for the tracer is in tank hull machineguns, of mostly out-dated tanks, where the machinegun operator cannot sight directly along the barrel, thus they have to rely on tracer bullets to guide their aim
Per i tank