[PyMOL] how to highlight some residues and make other residues being as background?

Dear all,In order to emphasize local interactions of several residues within a protein, I want to highlight these studied residues but make other residues vague and being as background. The setting "set fog, on" doesn't help much because the constrast between the studied residues and other residues is not strong. Could you help me with this problem? With many thanks.Yeping Sun
Institute of Microbiology, Chinese Academy of Sciences