A plasmonic optical spectrum filtering device is provided that filters electromagnetic waves by optical resonance, for example, by selective conversion between the free-space waves and spatially confined modes in plasmonic nano-resonators. Frequency-selective transmission and reflection spectra are engineered and can be used as spectrum filters for display and imaging applications. A thin film stack color filter is further disclosed, which can be designed to either function as a transmission color filter with efficiency twice that of conventional colorant based color filter; or as a reflective color filter for display devices (e.g., used in an energy harvesting reflective display). In other variations, a novel reflective colored display is viewable under direct sunlight, and can simultaneously harvest both incident light and generate electrical power. Methods of making such plasmonic optical spectrum filtering devices are also provided.