Srimad Bhagavatam, while describing the consorts of Lord Krishna, such as Srimati Rukmini and others, and the close associates of Lord Krishna such as the gopikas and the women in Mathura, frequently uses the motif of Kucha Kumkuma, i.e. kumkum or saffron powder smeared on the women's breasts.
Some instances are as follows:
In Bhagavatam 10.47, in Bhramara Gita, when Srimati Radharani addresses the Bee and indirectly talks to Uddhava, she mentions,
"O honeybee, O friend of a cheater, don’t touch My feet with your whiskers, which are smeared with the kuṅkuma that rubbed onto Kṛṣṇa’s garland when it was crushed by the breasts of a rival lover! Let Kṛṣṇa satisfy the women of Mathurā. One who sends a messenger like you will certainly be ridiculed in the Yadus’ assembly." SB 10.47.12
When describing Srimati Rukmini and Krishna's lovers' quarrel in 10.60, Shukabrahmam describes
With her tender foot, effulgent with the reddish glow of her nails, she scratched the ground, and tears darkened by her eye makeup sprinkled her kuṅkuma-reddened breasts. There she stood, face downward, her voice choked up by extreme sorrow. SB 10.60.23
Even the Mahabharata contains a similar motif in the Vana Parva, Chapter 12. When Draupadi laments about her plight to Krishna, Vaishampayana describes,
'Saying this the mild-speeched Krishna hid her face with her soft hands like the buds of lotus, and began to weep. And the tears of Panchali begot of grief washed her deep, plump and graceful breasts crowned with auspicious marks. Vana Parva 12
Though while not mentioning Kumkuma, he mentions auspicious marks.
Therefore, the question is, what exactly is the significance of this motif of Kumkuma smeared breasts, and was it a widespread practice in ancient Indian society?