Firefly

From PyroGuide

From Skylighter newsletter archive: "What is the Firefly effect? Firefly is an interesting effect. It is also called transformation. Perhaps my description of it will make clearer how it appears in the sky. It is generally a star or a comet whose effect consists of variations of charcoal orange (even red) mixed with twinkling silver flashes. The description "transformation" comes from the tendency of some firefly stars to begin as one color (orange from charcoal) and then to "transform" into twinkling silver. This delayed action ignition of the aluminum is caused by the firefly aluminum particles being so large that it takes ‘em awhile to get going."

References

http://www.skylighter.com/fireworks/How_to_make_sky_rockets/firefly_aluminum_rocket.asp
http://www.skylighter.com/fireworks/making_fireworks_projects/firefly_aluminum_fireworks_stars.asp