First, let’s go through the different centres called the chakras.
So, the first chakra at the bottom of the spine is called the Mooladhara and it is represented by a triangle with its apex down and the colour associated with it is yellow, the colour of the earth, and the triangle is placed in the middle of a square, a yellow square which again represents Prakriti or the material earth, the solid earth meaning energy at its grossest level of vibration.
The centre or Padma–chakras are also called padmas because they are like a lotus, which means just as the lotus blooms, the centre also blooms when the Kundalini energy touches them. So, they are also called padmas or lotuses.
So, the next lotus or the next chakra is called the Swadisthana chakra and it falls between the Mooladhara, which is the lowest and the Manipura chakra at the navel. The colour of Swadisthana is silvery like the moon, like moonlight and its symbol is a crescent moon.
Now, you’ll find this crescent moon on Goddess Durga’s head, and also on Lord Shiva‘s head touching his locks. It is the great tantric symbol of the astral world and subtle worlds, and its Tattwa is the principle of ‘aapas‘ or the principle of water.
Now the first chakra, the Mooladhara, represents Prakriti or the solid earth or solidity, and the next one we discussed, the Swadisthana, which is silvery and is shaped or symbolised by the crescent moon, represents the watery tattwa or the aapa tattwa, also called the ‘tejasa‘ or the dream tattwa. This is so because the energy called the Kundalini is ascending from the gross to the subtle–from solid state to the liquid state.
From solid to liquid to gaseous, the energy becomes subtler and subtler and the consciousness moves from gross to the subtle.
The next centre at the navel is known as the Manipura chakra. It is also known as the Kundalini chakra and it is represented by a triangle with its apex upwards. The colour given to it is the colour of fire, as red as fire, like a red-hot burning fire. This is the central part of the chakras where combustion takes place. Heat energy of the Kundalini is symbolised here and when the heat of the practice of Kundalini yoga emanates from the Manipura chakra, then the Kundalini rises further up, changing from liquid to the gaseous state while passing through the heat centre of the Manipura chakra.
The next centre in the centre of the chest is called the Anahatha chakra, and is represented by what is called the ‘Star of David’–two triangles intertwined or put together–one equilateral triangle pointing upwards and the other pointing downwards. The Anahatha chakra is coloured sky blue.
So from solid to liquid to gaseous, the energy has become subtler and subtler and the consciousness has moved from gross to the subtle.
The Anahatha chakra is also called the Anahath because when the mind is fixed on this centre, one hears the sound that is unstruck, the inner sound, the sound of ‘Om’ or Pranava that vibrates within this chakra when the mind or consciousness ascends to it.