Panel A: Halo C stars optically selected either through objective-prism plates or from optical photometry. The dotted lines indicate J − K =1.2, 2, and 3. The J − K =1.2 line is repeated in panels B, C, and D. Panel B: our 107 near-infrared (2MASS) selected C stars. Panel C: carbon stars discovered by Cruz and Reid during their survey for M, and L-type dwarfs; the colour domain searched by them is indicated by dash-dotted lines. Panel D: contaminants in our survey for halo C stars; most are M-type dwarfs, occasionally giants; a few non-M-type objects (L dwarfs, QSOs) are indicated by triangles. The solid line drawn in all panels is the best fit for all currently known halo C stars.