Developing color-tunable pure organic room-temperature phosphorescent (RTP) materials based on biopolymers is of great significance for efficient utilization of natural resources, yet still challenging. Herein, tunable multicolor phosphorescence emission, including white-light, is achieved in cellulose-based RTP materials by coorganizing complementary cyan and red organic phosphors into the strong hydrogen-bonding networks of cellulose. The non-radiative transition of phosphors can be effectively suppressed by the high density of hydrogen bonding among the cellulose chains as well as the covalent interaction. The difference in optical properties between the two phosphors enables the adjustment of the phosphorescence emission color of the material from green to cyan, white and then red. It is demonstrated that the designed material can be used as versatile inks for pattern drawing and information encryption, with favorable multicolor emission and excellent aqueous processability. Therefore, considering the biodegradability and sustainability of cellulose materials, cellulose-based RTP has enormous potential in advanced anti-counterfeiting and information encryption as eco-friendly phosphorescent inks and coatings.