Color–magnitude diagram (CMD) of the GD-1 stream of the 1958 stars, selected around the stream track (see Section 3.1 for details) and corrected for the distance variations (see Section 2 for details). The left and right lines represent the isochrones of M92 (with a shift of −0.025 in color) and M5 (with a shift of +0.025 in color), respectively. The red box is used to select BHBs of the GD-1 stream. The red dots mark the final selected stars of the GD-1 stream in the CMD.