The Elemental Realms are locations that serves as the center point or hub which connect and pervades various elements in the DC universe. They are ruled and maintained by immortal creatures called Elementals who are also considered as their guardians. Parliaments serves as the collective rulers of the realms.
For many elements, the Realms also serve as their consciousness. Realms such as the Green and the Clear acts similar to a brain for non-sentient beings such as plants and aquatic life.
The Green is an elemental force which connects all forms of plant life on earth, experienced by elementals as an ethereal realm inhabited by the collective minds of the Parliament of Trees. It is the realm of Swamp Thing and the Parliament of Trees.
Time and again, The Green has chosen protectors for itself to wield its power against threats to the earth or from opposing elemental forces such as The Red, The Clear, The Grey, and The Rot.
In the Earth-2 Universe, Green Lantern (Alan Scott) serves as the Green's guardian.
The Red is a force which connects and pervades all animal life in the universe. It is intended to be the force from which a number of animal-powered heroes get their abilities. Superheroes such as Animal Man and Vixen can tap into the Red. The Red and The Green have been allied in battling against The Rot for all time. Both have turned to humans to be their champions, as they are the most resilient. It is ruled mostly by the Parliament of Limbs who represent the interests of all animal life on the planet Earth
It was Hellblazer writer Jamie Delano who was one of the first to name and describe the Red during his run on Animal Man.
The Black or The Rot is a force which is strongly associated with death. The decay and rotting of living things is where it flourishes, with its base being in the "Bone Kingdom" at in the deadlands of the United States. As such, it works in opposition to life forces such as The Red and The Green. Like the other elemental forces of its kind, the Rot is guarded by a Parliament; the Parliament of Decay. Each member of this Parliament is a former Avatar of Death. The villain Anton Arcane is one of the agent of the Rot. The realm is ruled by the Parliament of Decay.
The Clear, sometimes called the Blue, is a force which connects and pervades all aquatic life and oceanic themed elements in general within the universe. It is intended to be the force from which a number of aquatic-themed heroes or villains acquire certain abilities. The Clear is heralded by the enigmatic Parliament of Waves, an ensemble of former avatars who now reside as a counselling order to the Clear.
Superheroes such as Aquaman, has access to the Clear that allows him to communicate with marine life, as well as utilize hydrokinetic abilities.
The Metal is a kingdom that gained sentience and cohesion in the 21st century, composed of mechanical intelligences of various sources, and focused in on a mechanical base known as Servus in the Arctic Circle. It is not the source of all metal-based abilities, but only those connected to The Rithm who serves as its parliament.
The Grey is the realm of fungus and other dying or doomed plant life. In most DC stories the Grey and the Black are sometimes mistaken or interchanged with each other.
Though The Green and The Grey coexisted in relative peace for a time, the dawn of man and its potential for destruction led Matango to tempt them with fruit from Tuuru, the Tree of Knowledge. The result prompted a war between the two life forces; a war which weakened both sides and forced the Parliament to leave the Garden of Eden to the ice and snow, and move to Brazil.