Colour-magnitude diagram in M_K1 vs. K1−K2 for all candidates in the BEAST first-epoch observations performed to date. The CCs are denoted with brown dots, while template objects representing various spectral types are indicated with different colours as shown in the legend. Previously discovered low-mass substellar companions that have been observed in the K1 and K2 filters are also shown as black and grey symbols. For relatively bright CCs, background stars can be distinguished from probable physical companions in most cases, but for fainter CCs, there is substantial overlap between the two populations in the diagram.