The world of the spirit starts where logic ends. Though logic, in the modern world, is the ultimate test of reason and the pinnacle of intelligent thought, minds on a higher plane see logic as lower intelligence limited by the boundaries of reason which is further limited by the limitations of the individuals buddhi. Which probably explains why every school of spiritualism or any mystical practice emphasises experience over analysis. Also, why the overtly questioning mind chatters incessantly only at the peripheries of the spirit-kingdom, seldom able to penetrate its very core. Forget the core. It cannot even unravel the first layer. However, since the current world speaks and comprehends only the tongue of logic, we shall try to understand the aura, a subject firmly embedded in the spirit realm in this context. All bodies emit heat radiation or vibrations. This is a superficial or logical explanation of what auras are and why they are constant or changing.
A lot of scientific study of the physical auras has been done by the Western countries in recent years and there is much about photographing the auras, and they have variously called it the human atmosphere force field, bio-energy and so on. The fundamental substance of which the aura is composed of is best described by the Sanskrit term, prana.
Prana is a deep subject; but let us for our present purposes understand it as the vital essence or force, which is the basis of all life. It is the steam that runs the physical and mental machinery of life. The colours of our mental states are manifested in the pranic substance of our auras just as the colours of chemicals are seen in water.
Logically, we can say that these colours are regulated at seven energy centres of the body called the chakras. Each of the chakras, mooladhar, swadhishthan, manipoorak, anahat, vishuddhi, ajna, and sahastrar vibrate at a particular colour frequency. Any imbalance that stays for too long becomes chronic and manifests as an ailment in the physical body. What the clairvoyant can see are the aura or chakra imbalances which are seen as the shade of the colour being too dark or heavy or colours other than the chakras own colour manifesting. Considerations like what shade is mixing with the natural colour, in what proportion, the positioning, the luminosity, etc. all determine the state of the being.