There is provided an ink composition that is excellent in anti-feathering and scratch resistance of markings and is suitable for industrial production. The present invention relates to: composite colored particles each including a resin particle carrying a positive electric charge on a particle surface and a pigment particle carrying a negative electric charge on a particle surface, the resin particle and the pigment particle forming a composite through electrostatic interaction; a water-based ink composition containing the composite colored particles dispersed in a water-based medium; and a writing instrument containing the water-based ink composition. Furthermore, the present invention relates to a method for producing composite colored particles, the method including forming a composite by mixing a resin emulsion containing resin particles each carrying a positive electric charge on a particle surface and a pigment dispersion containing pigment particles each carrying a negative electric charge on a particle surface.