A method of treating a substrate, comprising providing a substrate having a generally sheet or planar form or a fiber or yarn form; providing a colorant to be set at the surface of the substrate; and subjecting the substrate and colorant to reactive species from a plasma generated by an atmospheric plasma apparatus until the colorant is set at the surface of the substrate. A method of setting a colorant on a substrate, comprising performing an etch operation, or plasma pre-treatment to change surface charge, on a substrate using a plasma, particularly a plasma generated at atmospheric conditions, to create a desired surface texture, or surface charge, at the surface of substrate; and depositing a colorant on the surface under plasma or non-plasma conditions; and allowing the colorant to set at the surface of the substrate.