MSG (Multidimensional Stellar Grids) is a library that synthesizes astrophysical spectra and photometric colors via interpolation in pre-calculated grids. Given a set of stellar atmospheric parameters (e.g., effective temperature, gravity and metallicity), MSG can calculate the specific intensity of the emergent radiation field as a function of wavelength and angle. It can also convolve these data with appropriate filters and response functions, to evaluate colors in a wide variety of photometric systems.
Full documentation for MSG can be found at https://msg.readthedocs.io/en/stable.