Посмотрим доступные шаблоны

ls -1 /usr/share/nano/

asm.nanorc
awk.nanorc
cmake.nanorc
c.nanorc
css.nanorc
debian.nanorc
fortran.nanorc
gentoo.nanorc
groff.nanorc
html.nanorc
java.nanorc
makefile.nanorc
man.nanorc
mgp.nanorc
mutt.nanorc
nano-menu.xpm
nanorc.nanorc
objc.nanorc
ocaml.nanorc
patch.nanorc
perl.nanorc
php.nanorc
pov.nanorc
python.nanorc
ruby.nanorc
sh.nanorc
tcl.nanorc
tex.nanorc
xml.nanorc

Добавим их в конфигурацию nano
Для определенного пользователя:

nano ~/.nanorc

Для всех прользователей

nano /etc/nanorc

include "/usr/share/nano/asm.nanorc"
include "/usr/share/nano/awk.nanorc"
include "/usr/share/nano/cmake.nanorc"
include "/usr/share/nano/c.nanorc"
include "/usr/share/nano/css.nanorc"
include "/usr/share/nano/debian.nanorc"
include "/usr/share/nano/fortran.nanorc"
include "/usr/share/nano/gentoo.nanorc"
include "/usr/share/nano/groff.nanorc"
include "/usr/share/nano/html.nanorc"
include "/usr/share/nano/java.nanorc"
include "/usr/share/nano/makefile.nanorc"
include "/usr/share/nano/man.nanorc"
include "/usr/share/nano/mgp.nanorc"
include "/usr/share/nano/mutt.nanorc"
include "/usr/share/nano/nanorc.nanorc"
include "/usr/share/nano/objc.nanorc"
include "/usr/share/nano/ocaml.nanorc"
include "/usr/share/nano/patch.nanorc"
include "/usr/share/nano/perl.nanorc"
include "/usr/share/nano/php.nanorc"
include "/usr/share/nano/pov.nanorc"
include "/usr/share/nano/python.nanorc"
include "/usr/share/nano/ruby.nanorc"
include "/usr/share/nano/sh.nanorc"
include "/usr/share/nano/tcl.nanorc"
include "/usr/share/nano/tex.nanorc"
include "/usr/share/nano/xml.nanorc"

Подсветка синтаксиса в конфигурационных файлах

nano /usr/share/nano/conf.nanorc

Добавляем в него строки:

# config file highlighting

syntax "conf" "(\.(conf|config|cfg|cnf|rc|lst|list|defs|ini|desktop|mime|types|preset|cache|seat|service|htaccess)$|(^|/)(\w*crontab|mirrorlist|group|hosts|passwd|rpc|netconfig|shadow|fstab|inittab|inputrc|protocols|sudoers)$|conf.d/|.config/)"

# default text
color magenta "^.*$"
# special values
icolor brightblue "(^|\s|=)(default|true|false|on|off|yes|no)(\s|$)"
# keys
icolor cyan "^\s*(set\s+)?[A-Z0-9_\/\.\%\@+-]+\s*([:]|\>)"
# commands
color blue "^\s*set\s+\<"
# punctuation
color blue "[.]"
# numbers
color red "(^|\s|[[/:|<>(){}=,]|\])[-+]?[0-9](\.?[0-9])*%?($|\>)"
# keys
icolor cyan "^\s*(\$if )?([A-Z0-9_\/\.\%\@+-]|\s)+="
# punctuation
color blue "/"
color brightwhite "(\]|[()<>[{},;:=])"
color brightwhite "(^|\[|\{|\:)\s*-(\s|$)"
# section headings
icolor brightyellow "^\s*(\[([A-Z0-9_\.-]|\s)+\])+\s*$"
color brightcyan "^\s*((Sub)?Section\s*(=|\>)|End(Sub)?Section\s*$)"
color brightcyan "^\s*\$(end)?if(\s|$)"
# URLs
icolor green "\b(([A-Z]+://|www[.])[A-Z0-9/:#?&$=_\.\-]+)(\b|$| )"
# XML-like tags
icolor brightcyan "</?\w+((\s*\w+\s*=)?\s*("[^"]*"|'[^']*'|!?[A-Z0-9_:/]))*(\s*/)?>"
# strings
color yellow "\"(\\.|[^"])*\"" "'(\\.|[^'])*'"
# comments
color white "#.*$"
color blue "^\s*##.*$"
color white "^;.*$"
color white start="<!--" end="-->"

Добавляем строку в ~/.nanorc или в /etc/nanorc

include /usr/share/nano/conf.nanorc