On X11/Motif the default fonts and colors (and certain other properties) used in CAPI elements are determined by the applicable X resources.
To construct custom X resources for your CAPI/Motif application, consult the file
app-defaults/Lispworks
which is supplied in the LispWorks library for relevant platforms.This file contains the application fallback resources for LispWorks 5.0 and illustrates resources you may wish to change for your application.
The file
app-defaults/GcMonitor
contains the application fallback resources for the Lisp Monitor window. The files
app-defaults/*-classic
contain the fallback resources that were supplied with LispWorks 4.4.
For further information about X resources, consult documentation for the X Window system.