The ability to see a shimmering colour around either humans, or sometimes other living things, is a skill claimed by some new-age practitioners. Psychics and holistic medicine practitioners often claim to have the ability to see the size, color and type of vibration of an aura and use this to make judgments about the person's health, morals or wellbeing. As with many pseudoscientific concepts, it is loosely defined and varies across cultures and time. It was first popularized by Charles Webster Leadbeater, a former priest of the Church of England and a member of the mystic Theosophical Society, in the early 20th Century.
Leadbeatter wanted to use some mystical teachings he had learned in India to make scientific investigations about the world, and said that the aura illustrated the state of humans at various stages of their moral evolution, from the "savage" to the saint. Fellow Theosophists such as Rudolph Steiner (of schools fame) picked up his ideas of auras linking it to chakras and carried it into more mainstream circles, until it was eventually picked up by the New-Age movement in the late 20th C. A variety of New-Age books proposed different links between different chakras and colors of auras.
Of course it is all bullshit. Controlled experiments on people claiming to see auras fail to show any such ability. Several televised attempts were made and all fail miserably when controls such as placing subjects and mannequins behind an opaque screen (the reader says they can still see the aura around the person and should therefore be able to differentiate) are made. Some claims have been made that auras may be the result of synaesthesia. However, a study in 2012 discovered no link between them, concluding "the discrepancies found suggest that both phenomena are phenomenologically and behaviourally dissimilar." Clinical neurologist Steven Novella (of the Skeptics Guide to the Universe) has written "Given the weight of the evidence it seems that the connection between auras and synaesthesia is speculative and based on superficial similarities that are likely coincidental."