Each color on the map represents a separate colony of fungi growing upon the walls of the chapel; each colony is sentient and capable of speaking, but different colonies have varying motivations.
The blue fungus will lie to the characters and lure them to their deaths, tempting them with tales of riches in horrifically dangerous locations.
The green fungus will try to help the party with good advice (that of course won't be trusted because the green fungus speaks the truth in a voice that sounds like it peddles badly-told lies).
The yellow and purple colonies are at war with each other and try to bribe the party with promises of treasure to wipe out their foes.
The orange fungus will try to convert the characters to the worship of the Queen of Fungi; it has no other conversation than fungoid theology.
May Zuggtmoy smile upon thee and grow ever vaster in the dank darkness of thine heart!