I frequently use Mad Bull green tracer BBs during night games. I know red tracers are also available, but they're not as bright. If I'm not mistaken, those are the only two colours which can be activated with normal white light. Any other tracer BBs require an ultraviolet light source to activate them.
I use a Tokyo Marui tracer unit on the end of my rifle barrel. For those times I want to take a shot and not be detected, it's a simple matter to just turn off the tracer unit so the BBs don't glow. When I do fire off a burst of tracers in the middle of a night game, the result is spectacular!
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