The development of a simple and rapid technique to form structural colors would be an important step to achieve the coloring without dyes containing toxic organic dyes or heavy metals. Here, a novel method to form structural color using plasma etching is presented. The structural color is reproducibly formed by the plasma irradiation of the surface of a pencil lead for 40–120 s. The color changes with the plasma irradiation time. The formed colors exhibit a luster and turn blue, yellow, red‐purple, blue, green, or pale red by the plasma irradiation time of 40, 60, 80, 90, 100, and 120 s, respectively. The surface asperities due to the removals of the graphite at the surface of the pencil lead by the plasma etching are changed by the irradiation time. This causes the changes in the structural color of the pencil lead. The coloring by this method can easily control the colored part by using a masking plastic plate. Furthermore, a paper painted with a pencil is also colored by the plasma treatment. The presented method is a simple and rapid technique to form structural colors and can be applied for coloring without dyes.

The penciling part on a paper is colored by the formation of structural color, and the coloring of a paper without ink has been achieved. In a previous study, our group reported that structural color is formed by plasma irradiation (40–120 s) of the surface of a pencil lead or paper painted with a pencil. The formation of structural color due to the thin-layer interference of components of the pencil lead was observed. The clay exposed by removal of the surface graphite through plasma etching plays the role of a “thin layer”. The pencil lead can be colored blue, red, and green by the method. In the case of the paper painted with a pencil (6B), the paper turned blue but could not form the other colors by the method. The reason is that the graphite layer on the paper is not thick enough to form thin-layer interference to show colors other than blue. We now present the method that forms structural colors by plasma irradiation of the paper painted by a graphite-rich pencil lead (9B and 12B). The formation of various structural colors, such as blue, yellow, red-purple, and green, on the paper was achieved. The colored site can be effaced by an eraser. This method is a novel coloring method without using colored inks. This environmentallly friendly coloring method can be applied to various activities, such as studies and art, and can contribute to the achievement of a sustainable society.