Light Markers

Light Markers are apparently simple illuminatory devices mass produced by the Forerunner and used on their various installations. These small luminescent markers are theorized to be for guiding persons around while on one of the Halos. The original designers are the only ones who know their true purpose. There appear to be a number of different colors, including red, blue, and purple.

A single red marker is located on a tree at the ending of the level 343 Guilty Spark in Halo: Combat Evolved. It is noteworthy because Forerunner design rarely directly incorporates organic materials into it's architecture. This also indicates that that particular tree was around when Installation 04 was created, suggesting an extremely long lifespan and slow growth pattern of the trees found in that level.

Trivia
The Covenant-oriented lighters may have been reverse-engineered from the Forerunner ones, given because the Covenant copy and imitate rather than innovate and create.