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..."
Colours
"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;
Black lesya represents the lowest kind of state of mind. A person in this state of mind shows no compassion or mercy. People are afraid of them as these kinds of people are often violent. They also carry jealousy and animosity within themselves.
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
People in this blue lesya of mind are proud, haughty, and lazy. They are unreliable and other people avoid their company. They are cheaters, cowards, and hypocrites. These people also avoid all things religious.
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
Someone in grey lesya always remains sad and gloomy. They find faults in others and are vindictive. They boast about themselves, become excited over small matters, and lack mental balance.
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
People in red lesya are very careful about their actions and can discriminate between good and evil. They know the difference between what is right and what is wrong. They are kind, benevolent, religious, and lead a harmonious life.
A man who is humble, steadfast, free from deceit and inquisitiveness, well disciplined, restrained, attentive to his study and duties, who loves the Law and keeps it, who is afraid of forbidden things and strives after the highest good–a man of such habits develops the red leśyā.
— Uttarādhyayana-sūtra, 34.27:28
Lesyas depicted in Folio from Samghanayanarayna loose leaf manuscript (17th century) from Gujarat or Rajasthan
A person with yellow lesya is kind and benevolent and forgives everyone, even their enemies. They observe some austerities (mahavrata) and are vigilant in keeping their vows till their last breath. They remain unaffected by joys and sorrows.
"A man who has but little anger, pride, deceit, and greed, whose mind is at ease, who controls himself, who is attentive to his study and duties, who speaks but little, is calm, and subdues his senses–a man of such habits develops the yellow leśyā.
— Uttarādhyayana-sūtra, 34.29:30"
(wikipedia)