Lesya, according to the Jain theory of karma, is the coloring of the soul on account its association with the karmic matter. The colour of leśyā varies from person to person depending on the psychic states and mental activities behind an action. The coloring of the soul is explained through the analogy of crystal, that acquires the color of the matter associated with it. In the same way, the soul reflects the qualities of colour, taste, smell and touch of associated karmic matter, although it is usually the colour that is referred to when discussing the leśyās. Paul Dundas notes the key text expressing this Jain doctrine, explaining how the literary form of the text is helpful in dating and reconstructing the history of transmission.
A full statement of the theory of lesya occurs in chapter 34 of the Uttaradhyayana, one of the fundamental sutras of the scriptural canon. Inspection of the metrical structure there, which consists of a cluster of old sloka verses amplified by twice as many verses in the arya metre, makes clear that a great deal of ancient editorial care was taken to ensure that an original rudimentary description of this dimension of karma became fully cogent.
The ancient Jain text Uttarādhyayana-sūtra speaks of six main categories of leśyā represented by six colours – black (krishna), blue (neel), grey (kapot), red (tejo), yellow (padma) and white (shukla).Uttarādhyayana-sūtra describes the mental disposition of persons having black and white leśyās:
A man who acts on the impulse of the five sins, does not possess the three guptis, has not ceased to injure the six (kinds of living beings), commits cruel acts, is wicked and violent, is afraid of no consequences, is mischievous and does not subdue his senses – a man of such habits develops the black leśyā.
— Uttarādhyayana-sūtra, 34.21:22
A man of the following qualities: envy, anger, want of self-control, ignorance, deceit, want of modesty, greed, hatred, wickedness, carelessness, love of enjoyment; a man who pursues pleasures and does not abstain from sinful undertakings, who is wicked and violent – a man of such habits develops the blue leśyā.
— Uttarādhyayana-sūtra, 34.23:24
A man who is dishonest in words and acts, who is base, not upright, a dissembler and deceiver 3, a heretic, a vile man, a talker of hurtful and sinful things, a thief, and full of jealousy – a man of such habits develops the grey leśyā.
— Uttarādhyayana-sūtra, 34.25:26