  New Johnson-Cousins UBVRI photometry of giants in globular clusters is
combined with JHK photometry on the CIT system to produce color sequences for
giants from the globular clusters M3, M5, M13, and M92. UBVRI data are also
presented for giants in the metal-rich open cluster NGC 6791. These data fill a
gap in the literature, especially for the R & I bands. We provide the empirical
relations between broad band colors for various [Fe/H] values for metal-poor
giants. The color sequences for U-B and B-V show clear separations for
different [Fe/H] values. We also find weak, though 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_{eff}
relation is given.
