a better ruby.nanorc /usr/share/nano/ruby.nanorc

ruby.nanorc

## Here is an example for Ruby.
##
syntax "ruby" "(Gemfile|Rakefile|\.(rb|rake|gemspec|ru|simplecov))$"
header "^#!.*(env\s|\/)ruby[-0-9._]*"

## Asciibetical list of reserved words
color yellow "\<(BEGIN|END|alias|and|begin|break|case|class|def|defined\?|do|else|elsif|end|ensure|false|for|if|in|lambda|module|next|nil|not|or|redo|rescue|retry|return|self|super|then|true|undef|unless|until|when|while|yield)\>"
## Constants
color brightblue "(\$|@|@@)?\<[A-Z]+[0-9A-Z_a-z]*"

## Some unique things we want to stand out
color brightyellow "\<(__FILE__|__LINE__)\>"
## Regular expressions
color brightmagenta "/([^/]|(\\/))*/[iomx]*" "%r\{([^}]|(\\}))*\}[iomx]*"
## Shell command expansion is in `backticks` or like %x{this}.  These are
## "double-quotish" (to use a perlism).
color brightblue "`[^`]*`" "%x\{[^}]*\}"

#---
##+ Ruby "symbols"
##+ must be above Constants Chain, below Strings it will make :"some symbol" will work
icolor magenta ":(\"|'|@|@@)?([0-9A-Z_>]+(\"|'|\?)?|(\[\]))" "(\"|'|@|@@)?[0-9A-Za-z_>]+(\"|'|\?|\!)?:"

## Ruby "symbols" (original)
#icolor magenta "([     ]|^):[0-9A-Z_]+\>"
## Variables
icolor brightblue "(\$|@|@@)\<[0-9A-Z_]*"

## Strings, double-quoted
color green ""([^"]|(\\"))*"" "%[QW]?\{[^}]*\}" "%[QW]?\([^)]*\)" "%[QW]?<[^>]*>" "%[QW]?\[[^]]*\]" "%[QW]?\$[^$]*\$" "%[QW]?\^[^^]*\^" "%[QW]?![^!]*!"
## Expression substitution.  These go inside double-quoted strings,
## "like #{this}".
color brightgreen "#\{[^}]*\}"
## Strings, single-quoted
color green "'([^']|(\\'))*'" "%[qw]\{[^}]*\}" "%[qw]\([^)]*\)" "%[qw]<[^>]*>" "%[qw]\[[^]]*\]" "%[qw]\$[^$]*\$" "%[qw]\^[^^]*\^" "%[qw]![^!]*!"

## symbols % syntax
color magenta "%[i]?\{[^}]*\}" "%i?\([^)]*\)" "%[i]?<[^>]*>" "%[i]?\[[^]]*\]" "%[i]?\$[^$]*\$" "%[i]?\^[^^]*\^" "%[i]?![^!]*!"

##+ Constants chain
##+ this colors the :: as well, otherwise it show some pink
##+ because of symbol and this overwrites it
color brightblue "::[A-Z]+[A-Za-z0-9_]+?" "[A-Z]+[A-Za-z0-9_]+?::"
##+ (reset some of the color that gets 'written' due to lack of lookahead)
##+ method
color white "::[a-z][A-Za-z0-9_]+"
#---

## block Comments
## place above the normal Comments section
color cyan start="^=begin" end="^=end"
## Comments
color cyan "#[^{].*$" "#$"
color brightcyan "##[^{].*$" "##$"
## "Here" docs
color green start="<<-?'?EOT'?" end="^EOT"
## Some common markers
color brightcyan "(XXX|TODO|FIXME|\?\?\?)"

##+ Trailing whitespace
color ,green "[[:space:]]+$"

+ for lines added, and some spaces for clarity