Color–color selection process. Left: 2D histogram of approximately 17 988 392 sources obtained from four ADQL queries to the Gaia services and a WISE cross-match. The first selection cut was applied in the Gaia color–color diagram using a linear regression in logarithmic scale, resulting in the removal of 143 434 sources. Confirmed SySts are marked as orange stars. Right: 2D histogram of over 4 million sources selected from the 2MASS color–color diagram. The color bar indicates the number of sources per bin in logarithmic scale for both panels.