You use command line, as root user.
Then I found the easiest way to restart X was to exit CDE and relaunch CDE.
For Solaris x86, review the man page for kdmconfig.
For Solaris SPARC, review the appropriate man page for
whichever utility is appropriate for the frame buffer chipset.
( fbconfig, afbconfig, pfbconfig, m64config, ffbconfig, etc )