M_map plot values greater than a threshold

Hi all,

I have some problems with a m_pcolor map on Matlba.

I have a map with values of velocity of water currents. I would like to overlay the bathymetri so the land apperas in a fixed color.

I already have try with the contour of bathimetri = 0 (the contour pf the coast), but I would like to colored all the coast.

How can I do to just overlay in a m_pcolor the values of bathymetri grater than 0 and the values smaller appear transparent (so I can see the values of velocity)??

Something like mist=m_pcolor(bat_lon,bat_lat,batimetria([0,1000]),shading interp, colormap grey ????

Thank you and sorry for my english,

Miguel