The determination of metal abundances for individual giants from Washington photometry is revised, with several significant improvements incorporated. The solar-abundance two-color relations are revamped with the inclusion of new observations of a large sample of solar-abundance giants with small reddenings, especially those with late-K spectral types. The new relations are very similar to the original ones derived in C76 except for a zero-point offset. A new temperature index, M-T2, is investigated, as well as a new abundance index, C-T1, in addition to the standard indices. The M-T2 index has a much broader baseline and thus a much larger range than T1-T2, and is therefore less susceptible to photometric errors. The significant decrease in abundance sensitivity for cooler stars, suspected by previous investigations, is confirmed by including observations of a number of giants with a range in temperature in each of a large sample of open and globular clusters. A procedure for correcting the abundance indices for cool stars is derived which significantly improves the metallicity determination.