The third tab under Environment contains the Styles options.
Figure 3.4 The Styles tab of the Environment Preferences
By default the editor uses a system default font. You can choose an alternative font and see a sample of it displayed in the Editor Font area. Click in the Sample: area to raise a font chooser. After you select the font, the text "Click here to choose the font" is displayed in your selected font.
To make the LispWorks editor actually use your alternative font, select Override the system default font .
This specifies the font used in Editor and Listener windows and all other tools based on the editor, such as the Shell, Stepper and Profiler tools.
If you deselect Override the system default font the system remembers your choice of alternative font, but does not actually use it for display.
LispWorks IDE User Guide (Macintosh version) - 25 Nov 2011