Comparisons between color-color diagrams of OH/IR stars with/out IR flux and/or galactic position constraints show that little of the color dispersion is innate: the most precise colors come from high flux samples away from the Galactic Center. It is advantageous to delineate the color range of O-rich shells by only color selecting objects in the IRAS Point Source Catalog (PSC) with S(25) > 100 Jy, which yields 333 objects. All but 2 of these have published LRS spectra, which often suffice to determine whether an object is carbon or oxygen rich. About 80% of them have been searched for 1612 MHz masers, and ≈70% for SiO, water and/or mainline OH masers. As bright objects, most “oddballs” have been investigated at other wavelengths too. This data, together with information gleaned from a SIMBAD search, was then used to distinguish emission-line, T Tauri and carbon stars from the predominent residuum of O-rich shells.