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Updated uvby observations for a larger sample of metal-deficient red giants are presented and combined with a select sample of data from the literature transformed to a common system. Using the reddening maps of Burstein the dispersion among the residuals for 58 giants is +/- 0.16 dex. The dereddened indices are used to show that for red giants with (Fe/H) less than -1.5, there is a well-defined relation in the c0, (b-y)0 diagram which exhibits only a weak dependence upon metallicity. Use of the standard relations allows one to obtain reddening estimates for normal halo field giants and globular clusters in the appropriate metallicity range.
Anthony-Twarog et al. (Fri,) studied this question.