Left: NIR color-magnitude diagram of the upper limits derived from our X-shooter spectra (see Appendix C). Error bars are omitted for clarity, but they may be found in Appendix C; the typical error is ∼0.6 mag. The gray lines link our upper limit with the literature values (gray dots and arrows). All of the other lines are the same as in Fig. 2. We note that the color is composed of a subtraction of two upper limits and, therefore, it is uncertain. Right: optical color-magnitude diagram of the upper limit photometric points. In the VIS range, the photometric upper limits are well below the reddening line. Again the color is composed of a subtraction of two upper limits and, therefore, it is uncertain.