In the title of this Symposium: "The rise and fall of star formation in galaxies", the "falling" stage is mostly represented by so-called Green Valley galaxies. In this phase, quenching mechanisms operate, concerning the evolution from star formation towards quiescence. Therefore, GV galaxies are ideal laboratories to test cosmological simulations. This contribution focuses on the application of a novel, dust-independent, definition of the GV, to two of the most recent simulations: EAGLE and Illustris-TNG. We present some of the results, concerning the excess fraction of quenched galaxies in simulations, with respect to observational data from SDSS. We suggest possible causes for the mismatch.