  We build a theoretical picture of how the light from galaxies evolves across
cosmic time. In particular, we predict the evolution of the galaxy spectral
energy distribution (SED) by carefully integrating the star formation and metal
enrichment histories of semi-analytic model (SAM) galaxies and combining these
with stellar population synthesis models which we call mentari. Our SAM
combines prescriptions to model the interplay between gas accretion, star
formation, feedback process, and chemical enrichment in galaxy evolution. From
this, the SED of any simulated galaxy at any point in its history can be
constructed and compared with telescope data to reverse engineer the various
physical processes that may have led to a particular set of observations. The
synthetic SEDs of millions of simulated galaxies from mentari can cover
wavelengths from the far UV to infrared, and thus can tell a near complete
story of the history of galaxy evolution. \keywords{galaxies: evolution -
galaxies: stellar content - galaxies.}
