Oki C5300n User Manual page 98

Once a custom gamma adjustment has been made, the settings can
be saved to the printer's PPD (PostScript Printer Description) file, and
can be selected from the Printer Driver Colour options.
Creating a Gamma Adjustment, Step-by-step
Ensure that your Oki printer is selected as default on your Desktop.
1. You can do this by selecting the printer icon, and from the
Printing menu select Set Default Printer.
2. Launch the Oki PostScript Utility.
3. From the Utilities menu, select Adjust Printer Gamma....
MAC OS 9.X / CLASSIC > 98