The present invention provides a method of changing color or transmittance of light on a surface part of an object. The surface part of the object includes a solvent and a plurality of particles dispersed in the solvent. When electric field is applied to the solvent and the plurality of particles, the transmittance of color or light on the surface part of the object is changed due to the change of the inter-particle distances or the positions of the particles, according to the magnitude, direction, application time or application frequency of electric field, wherein the magnitude, direction, application time or application frequency of electric field are changed by associating the input signal by the user of the object or the signal acquired by the object or the signal acquired by the sensing unit provided to the object.