Colors of Class III stars vs. effective temperature. Blue horizontal lines plot (U − J), red crosses (U − I), green 45 deg lines (U − R), cyan –45 deg lines (U − V), as labeled. The solid lines show the best fit, the dashed lines  ± 2σ. In the text, we will define the region between the dashed lines as the photospheric strip. (A color version of this figure is available in the online journal.)