Red points are TGAS stars that have ṽ_y < 50 km s⁻¹ and are not tagged as halo by our classifier, despite having halo kinematics. Those stars are found to have redder G− K colours than expected for metal-poor halo stars. It is possible that these stars belong to the metal-poor tail of the thick disk. The grey points (bottom panel) have M_K magnitudes brighter than the cut marked by the black dashed line (top panel) and are not labelled as halo by our classifier. Even though they have colours consistent with those of metal-poor stars, the kinematics of the vast majority of these sources is purely consistent with that of disk stars.