The Karma of a Yogin is neither white nor black. That of others is threefold.
When the Yogin is in the state of Samadhi, the state of enstasy where all mind fluctuations have come to a halt, no Karma can accrue or sprout. This is the state called Yoga or union with the Self Within.
The mind with its Vrittis or activity and fluctuations over time create impressions, a groove so to speak in the subconscious mind which when watered by the emotions propel one to action and a certain destiny—a reaction or Karma that is threefold: white when deemed favorable, black when deemed unfavorable and mixed when it is an admixture of favorable and unfavorable.
As the adage goes:
Sow a thought
Reap and action;
Sow an act
Reap a habit;
Sow a habit
Reap a character;
Sow a character
Reap a destiny.
A destiny hence begins with a thought for better or for worse. This is why Krishna in the Bhagavad Gita states to Arjuna: ‘You have a right to action / work but not to the fruits thereof’.
It is all a matter of intention. Hence the importance of detachment to outcome.
Only in Nishkama Karma, disinterested action, can one go beyond white, black or mixed reactions and do one’s Dharma perfectly.