Structural colors based on nanostructured surfaces are an environmentally friendly alternative to dyes and pigments. In this study, structural colors were produced by spherical silica nanoparticles. By controlling the size of the spherical silica nanoparticles, the changes in color were controlled. The sizes of the nanoparticles were controlled by adjusting the ammonia content in the conventional Stöber method. Spherical silica nanoparticle powders were obtained using a centrifuge and an ultrasonic grinder oven, which were subsequently dispersed in deionized water and alcohol for dip coating. The particle sizes of the samples increased with increase in the amount of ammonia used in the synthesis process and were not affected by the dip coating. Spherical silica nanoparticles were uniformly arranged on the surface of the glass slides for all the samples studied. Thus, the structural colors produced by the spherical silica nanoparticles changed according to the particle size, which can be controlled by the ammonia content during synthesis.