Silver nanoparticles (AgNPs), the color of which originates from localized surface plasmon resonance (LSPR), are applied to the yellow pigment for stained glass. In this study, we synthesized AgNPs with different particle sizes via the thermal decomposition of silver oxalate and dispersed them in 1-butanol by using a phosphate ester as a dispersant. This dispersion was applied to a polyvinyl chloride film, and its color was examined. Consequently, a novel method that can control a* and b* in the CIE 1976 L*a*b* color space by optimizing the size and dispersant of AgNPs was developed. The proposed color control method realizes color expressions, such as gold and copper.