Top: magnitude histograms for early-type star candidates (green) and stars more than 2-σbluer than the RGB (see Fig. 6). This shows that the number of stars at the redder side (earlier spectral type) of the RGB is clearly larger than that at the bluer side (later spectral type). Bottom: ratio of the bluer stars to the early-type star candidates. If we assume that the bluer stars are red giants with a large photometric uncertainty, a similar number of stars may contaminate our sample of the early-type star candidates. So this diagram shows the expected ratio of such contamination for the candidates. The uncertainties in the top panel are given by the square root of the counts in each bin. For stars brighter than [2.25] = 12.25 mag, the contamination is low (≲ 25%).