From luminosity functions to colour distributions: tackling the next challenge in cosmological simulations

Galaxy spectral energy distributions (SED) remain among the most challenging and informative of the direct observables to reproduce in simulations, due to the large and complex mixture of physical processes that shape the radiation output of a galaxy. With the increasing number of surveys utilizing broadband colours as part of their target selection criteria, the production of physically-motivated realistic SED in simulations becomes necessary also for assisting in survey design. The recent successes in the reproduction of observed luminosity functions from far-ultraviolet to far-infrared represent a critical step towards better galaxy colour predictions. Here I will present that with the latest implementation of Shark, a state-of-the-art, open-source SAM, and ProSpect+Viperfish, a SED generator suite, we can closely reproduce the optical colours distributions observed in both the Galaxy And Mass Assembly (GAMA) survey and the Deep Extragalactic Visible Legacy Survey (DEVILS). I will specifically explore how the treatment of feedback, stellar formation, radiation re-processing by dust and central-satellite interactions have proven critical for this achievement