[Chimera-users] Chimera electrostatic potential

Hi, I've been unable to figure out how to colour the electrostatic surface of a protein red/white/blue. I'm assuming that you have to some how assign electrostatic potential before colouring but how is this done? I'm using a Mac and I've tried to use apbs with pymol but it will not recognise my pqr file generated on the pdb2pqr server or generate it itself. Thanks, Kate