We adopted uvby Strömgren photometry to investigate the metallicity distribution of \omega Cen Red Giant ( RG ) stars .
We provided a new empirical calibration of the Strömgren m _ { 1 } \equiv ( v - b ) - ( b - y ) metallicity index based on cluster stars .
The new calibration has been applied to a sample of \omega Cen RGs .
The shape of the estimated metallicity distribution is clearly asymmetric , with a sharp cut-off at low metallicities ( [ Fe / H ] < -2.0 ) and a metal-rich tail up to [ Fe / H ] \sim 0.0 .
Two main metallicity peaks have been identified , around [ Fe / H ] \approx -1.9 and -1.3 dex , and a metal-rich shoulder at \approx -0.2 dex .