Nanoscale phenomena are under increasingly intense investigation both in academia and industry. The unique physical and chemical properties stemming from their high surface area and confined space lead to properties that are distinct from atomic and bulk materials. Students need experience in nanoscience to enter this growing field of nanoscience research. This laboratory experiment introduces the optical properties of noble metal nanoparticles and probes the effect that the metal composition has on these properties. An aqueous synthesis is performed, which allows for the control of the alloy composition of Au/Ag nanoparticles, while minimizing costs and hazardous waste. The composition of the synthesized particles is verified by mass analysis. Extinction spectra are recorded experimentally and determined "in silico." The experimental and theoretical spectra are compared, and students are asked to identify causes for discrepancies on the basis of mass and particle size analysis. Students actively engage in identifying how the dielectric function of a nanoparticle affects the optical properties. By performing these experiments, students gain practical knowledge of the synthesis and characterization of metal nanoparticles, as well as an initial introduction to elements of theoretical chemistry. This experiment has been found to be easily reproducible; it utilizes primarily nonhazardous, nontoxic, green materials, and it can be performed with minimal added costs to normal budgets for lab courses.