Pattachitra is a general term for traditional, cloth-based scroll painting. In Sanskrit, Patta stands for "cloth" and "Chitra" for "picture". While in the context of Bengal tradition, Patachitra means “the paintings made by Patuas using natural colours.” According to legends, the art was originated among a group of artisans called ‘Patuas’ from Kalighat in the 19th century. They used to paint long narrative stories on scrolls of handmade paper often stretched to over 20 feet in length.
The colours used for this art are mainly derived from natural ingredients like leaves, seeds, roots, pulses, fruits, etc. For example, yellow colour from turmeric root, blue from Aparajita flower petals, black from the soot obtained after burning an oil lamp under a pot, etc. Along with the colours, the gum of Bael fruit is mixed so as to hold the paint on the base material. One of the famous modern artists involved in Kalighat Pattachitra is Jamini Roy, who experimented immensely with the painting during his early days of the occupation.
For more details:
https://www.dsource.in/resource/making-kalighat-pattachitra-kolkata