Normal tracer rounds work by using a small pyrotechnic charge ignited by burning powder that burns brightly, which makes the projectile visible to the naked eye even in daylight. the problem is this makes normal tracers basically flaming bullets that set things on fire.
Ammo Incorporated has unveiled a new “cold tracer” known as Streak Visual Ammunition. These non-flammable rounds produce a visible light visible to the shooter and anyone within a 30° viewing area from the bullet’s path.The rounds are currently available in 9mm, .40 S&W, and .45 ACP with prices starting around $12.99 for a box of 20.
Here is a video of them in action.