Target selection for our MMT survey for XMPGs. (a) Color–color plot showing all SDSS DR4 galaxies (dots) and the color-redshift track for the XMPG J0809+1729 (solid line). (b)–(d) Color-redshift plots showing SDSS objects (dots) that simultaneously match all three color-redshift tracks (solid lines) within 0.1 mag. After removing saturated stars and nearby H ii regions by visual inspection, we are left with a sample of 38 XMPG candidates (×). Four new XMPGs discovered by this survey are indicated by stars.