[sudosysgen]

A great spectral ray tracing engine is LuxRender : https://luxcorerender.org/ (the older one, that is - the newer LuxCore renderer does not have full spectral support)

Beyond the effects shown here, there are other benefits to spectral rendering - if done using light tracing, it allows you to change color, spectrum and intensity of light sources after the fact. It also makes indirect lighting much more accurate in many scenes.