Euclid's three dimensional reconstruction of the matter distribution in the Universe heavily relies on a proper calibration of the color-redshift relation. Getting such calibration was the motivation of the project Complete Calibration of the Color-Redshift Relation (C3R2) survey (Masters et al. 2017), with the goal of mapping the empirical relation between galaxy redshift and colors to the Euclid depth of i∼24.5(AB). The survey strategy is based on the fact that the diversity in observed galaxy colors at a given survey depth is limited and on the assumption that there exists a well-defined, mostly non-degenerate relation between a galaxy's position in multi-color space and its redshift, which can be traced empirically. The programme involved the spectroscopic observation of a few thousand of galaxies using the telescopes Keck, VLT and GTC. Here, we present the status, results and plans to complete the participation of our group in such project.