I have a new iMac. The printer default is set for color, and I'm catching hell at work for doing so much unnecessary color printing. How can I change the default to black, while allowing myself the option to print in color from time to time?

When you print and select the printer look through the options for the printer often the print driver will display several options like a choice to print in gray scale. Not knowing what printer or driver you are using I can not be more specific