Você precisará adicionar esta linha ao seu arquivo ~/.xxxterm.conf
:
userstyle_global = 1
De man xxxterm
xxxterm tries to open the user specific file, ~/.xxxterm.conf. If that file
is unavailable, it then uses built-in defaults.
The format of the file is <keyword> = <setting>. For example:
http_proxy = http://127.0.0.1:8080
Enabling or disabling an option is done by using 1 or 0 respectively.
[...]
userstyle_global When enabled new tabs will automatically
be displayed in low contrast mode.