The blue to red supergiant ratio in young clusters at various metallicities

We present new determinations of the blue to red supergiant ratio (B=R) in young open clusters at various metallicities. For this purpose, we examine the HR diagrams of 45 clusters in the Galaxy and of 4 clusters in the Magellanic Clouds. The identication of supergiants is based on spectroscopic measurements (with photometric counts to check the results). The new counts conrm the increase of the B=R ratio when the metallicity increases with the following normalized relation: B=R (B=R) = 0:05 e