XX Tri light, color, and temperature curves. a) V data (dots) and their fits with a trend (dashed line), with co-added modulations of timescales of 6 yr and 12 yr (line). Dotted line shows the cyclic term from the fit of the V − I_C data. b) B − V (upper dots) and U − B (lower dots). The U − B data were artificially shifted by +065 for easier presentation. c) V − I_C data (dots) and their fits with a trend (dashed line), and with co-added modulation on a timescale of ≈6.5 yr (line). The seasonal average comp-check values are plotted (shifted by +164 for presentation purpose) measured in the same time, and d) effective temperatures from V − I_C at maxima (triangles, overplotted with the 6.5 yr cycle originating from the V − I_C fit) and minima (squares) of the light curves. See text for details.