Do you wish to do this under program control or as a global change to your terminal session?
Under program control you can use ANSI escape sequences, but their interpretation may be different based on platform. Unfortunately, italics doesn't seem to be a supported option. Try:
for i=1:1:108 w $C(27)_"["_i_"mText Attribute - "_i_$C(27)_"[0m"_$C(13,10)
to see what you get. On Windows, I don't see any changes after 84, but on Linux (csession) I see additional color options from 90-107.
For the session, using the Windows version of Terminal:
If you're referring to csession under Unix/Linux, font selection will be a function of your terminal emulator.