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We present new determinations of the blue to red supergiant ratio ($B/R$) inyoung open clusters at various metallicities. For this purpose, we examine theHR diagrams of 45 clusters in the Galaxy and of 4 clusters in the MagellanicClouds. The identification of supergiants is based on spectroscopicmeasurements (with photometric counts to check the results). The new countsconfirm the increase of the $B/R$ ratio when the metallicity increases with thefollowing normalized relation : $\frac{B/R}{(B/R)_{\odot}} \cong 0.05\cdot e^{3\frac{Z}{Z_{\odot}}}$, where $Z_{\odot}=0.02$ and $(B/R)_{\odot}$ is the valueof $B/R$ at $Z_{\odot}$ which depends on the definition of $B$ and $R$ and onthe age interval considered (e.g. for spectroscopic counts including clusterswith $\log age$ between 6.8 and 7.5, $(B/R)_{\odot}\cong3$ when $B$ includes O,B and A supergiants).Comment: 7 pages, 2 figures. accepted for publication in A&

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