Ag nanoparticles (AgNPs) solutions were prepared and grown by photochemical reaction using white light sources, specifically such as a Xe lamp, the sunlight, and an incandescent lamp. Dichroism, also called the "Lycurgus effect", was observed in the obtained AgNPs solutions that were irradiated with white light for several days. The color of the transmitted light through the AgNPs solutions that were irradiated with the Xe lamp, the sunlight, and the incandescent lamp were orange, red, and blue, respectively, whereas the color of scattered light was greenish in all the samples. Based on the results of the transmittance, reflectance spectra, and scanning electron microscope images, the dichroic phenomenon is mainly caused by localized surface plasmon resonance light scattering of large triangular prismatic and decahedral AgNPs. In addition, we successfully prepared a dried silica gel that contains AgNPs with a dichroic property similar to the Lycurgus cup. This was fabricated by the solidification of the AgNPs solutions that were prepared under sunlight irradiation by a sol-gel method.