/usr/lib/ruby/ is in ruby-rainbow 2.0.0-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/rainbow/
/usr/lib/ruby/vendor_ruby/rainbow/legacy.rb
/usr/lib/ruby/vendor_ruby/rainbow/ext/
/usr/lib/ruby/vendor_ruby/rainbow/ext/string.rb
/usr/lib/ruby/vendor_ruby/rainbow/null_presenter.rb
/usr/lib/ruby/vendor_ruby/rainbow/color.rb
/usr/lib/ruby/vendor_ruby/rainbow/string_utils.rb
/usr/lib/ruby/vendor_ruby/rainbow/global.rb
/usr/lib/ruby/vendor_ruby/rainbow/version.rb
/usr/lib/ruby/vendor_ruby/rainbow/wrapper.rb
/usr/lib/ruby/vendor_ruby/rainbow/presenter.rb
/usr/lib/ruby/vendor_ruby/rainbow.rb