COLOR-COLOR RELATIONS FOR RED GIANTS IN STAR-CLUSTERS

New Johnson-Cousins UBVRI photometry of giants in globular clusters is combined with JHK photometry on the CIT system to produce color seque nces for giants from the globular clusters M3, M5, M13, and M92,. UBVR I data are also presented for giants in the metal-rich open cluster NG C 6791. These data fill a gap in the literature, especially for the R and I bands. We provide the empirical relations between broadband colo rs for various [Fe/H] values for metal-poor giants. The color sequence s for U - B and B - V show clear separations for different [Fe/H] valu es. We also find weak, although unexpected, metallicity dependences of V - R, V - I, and J - K colors. H - K is metal insensitive. The above colors are plotted as a function of V-K, and a literature (V- K)-T-ef f relation is given.