Forerunner symbols

In the halo universe, there are signs above doors, on Elite armour, virtaly anywhere on the halos, and in the Covenant. but what do the symbols meen?

According to a drawring by some members of the Bungie namely 'J.S', The blue and red signs mean a 'safe zone' as in wether or not the flood are there. There are symbols that can be used to write down names, when creating new users. This type is better when on Halo:Combat evolved, as the halo2 versions are usualy locked?