diff --git a/bin/miam b/bin/miam
index 6735bb1..27a4a33 100755
--- a/bin/miam
+++ b/bin/miam
@@ -92,7 +92,7 @@ ARGV.options do |opt|
   end
 end
 
-String.colorize = options[:color]
+Miam::StringHelper.colorize = options[:color]
 
 if options[:debug]
   Aws.config.update(
@@ -181,14 +181,14 @@ begin
 
     updated = client.apply(file)
 
-    logger.info('No change'.intense_blue) unless updated
+    logger.info(Miam::StringHelper.intense_blue('No change')) unless updated
   end
 rescue => e
   if options[:debug]
     raise e
   else
-    $stderr.puts("[ERROR] #{e.message}".red)
-    $stderr.puts(e.backtrace.map(&:yellow)) if options[:show_backtrace]
+    $stderr.puts(Miam::StringHelper.red("[ERROR] #{e.message}"))
+    $stderr.puts(e.backtrace.map { |bt| Miam::StringHelper.yellow(bt) }) if options[:show_backtrace]
     exit 1
   end
 end
diff --git a/lib/miam.rb b/lib/miam.rb
index 0ecd1e6..f2e0386 100644
--- a/lib/miam.rb
+++ b/lib/miam.rb
@@ -15,7 +15,7 @@
 require 'hashie'
 
 module Miam; end
-require 'miam/ext/string_ext'
+require 'miam/string_helper'
 require 'miam/ext/hash_ext'
 require 'miam/logger'
 require 'miam/template_helper'
diff --git a/lib/miam/driver.rb b/lib/miam/driver.rb
index 1e18043..a6dbbdc 100644
--- a/lib/miam/driver.rb
+++ b/lib/miam/driver.rb
@@ -107,7 +107,7 @@ def update_login_profile(user_name, attrs, old_attrs)
     log_attrs.delete(:password)
 
     log(:info, "Update User `#{user_name}`", :color => :green)
-    log(:info, "  login profile:\n".green + Miam::Utils.diff(old_attrs, attrs, :color => @options[:color], :indent => '    '), :color => false)
+    log(:info, Miam::StringHelper.green("  login profile:\n") + Miam::Utils.diff(old_attrs, attrs, :color => @options[:color], :indent => '    '), :color => false)
 
     unless_dry_run do
       @iam.update_login_profile(attrs.merge(:user_name => user_name))
@@ -287,13 +287,13 @@ def delete_instance_profile(instance_profile_name, attrs, roles_in_instance_prof
 
   def update_name(type, user_or_group_name, new_name)
     log(:info, "Update #{Miam::Utils.camelize(type.to_s)} `#{user_or_group_name}`", :color => :green)
-    log(:info, "  name:\n".green + Miam::Utils.diff(user_or_group_name, new_name, :color => @options[:color], :indent => '    '), :color => false)
+    log(:info, Miam::StringHelper.green("  name:\n") + Miam::Utils.diff(user_or_group_name, new_name, :color => @options[:color], :indent => '    '), :color => false)
     update_user_or_group(type, user_or_group_name, "new_#{type}_name".to_sym => new_name)
   end
 
   def update_path(type, user_or_group_name, new_path, old_path)
     log(:info, "Update #{Miam::Utils.camelize(type.to_s)} `#{user_or_group_name}`", :color => :green)
-    log(:info, "  path:\n".green + Miam::Utils.diff(old_path, new_path, :color => @options[:color], :indent => '    '), :color => false)
+    log(:info, Miam::StringHelper.green("  path:\n") + Miam::Utils.diff(old_path, new_path, :color => @options[:color], :indent => '    '), :color => false)
     update_user_or_group(type, user_or_group_name, :new_path => new_path)
   end
 
diff --git a/lib/miam/ext/string_ext.rb b/lib/miam/ext/string_ext.rb
deleted file mode 100644
index 32e0b30..0000000
--- a/lib/miam/ext/string_ext.rb
+++ /dev/null
@@ -1,25 +0,0 @@
-class String
-  @@colorize = false
-
-  class << self
-    def colorize=(value)
-      @@colorize = value
-    end
-
-    def colorize
-      @@colorize
-    end
-  end # of class methods
-
-  Term::ANSIColor::Attribute.named_attributes.map do |attribute|
-    class_eval(<<-EOS, __FILE__, __LINE__ + 1)
-      def #{attribute.name}
-        if @@colorize
-          Term::ANSIColor.send(#{attribute.name.inspect}, self)
-        else
-          self
-        end
-      end
-    EOS
-  end
-end
diff --git a/lib/miam/logger.rb b/lib/miam/logger.rb
index f127aea..129cafb 100644
--- a/lib/miam/logger.rb
+++ b/lib/miam/logger.rb
@@ -19,7 +19,7 @@ module Helper
     def log(level, message, log_options = {})
       message = "[#{level.to_s.upcase}] #{message}" unless level == :info
       message << ' (dry-run)' if @options[:dry_run]
-      message = message.send(log_options[:color]) if log_options[:color]
+      message = Miam::StringHelper.public_send(log_options[:color], message) if log_options[:color]
       logger = @options[:logger] || Miam::Logger.instance
       logger.send(level, message)
     end
diff --git a/lib/miam/string_helper.rb b/lib/miam/string_helper.rb
new file mode 100644
index 0000000..4b836f4
--- /dev/null
+++ b/lib/miam/string_helper.rb
@@ -0,0 +1,25 @@
+module Miam
+  module StringHelper
+    @colorize = false
+
+    class << self
+      def colorize=(value)
+        @colorize = value
+      end
+
+      def colorize
+        @colorize
+      end
+
+      Term::ANSIColor::Attribute.named_attributes.map do |attribute|
+        define_method(attribute.name) do |str|
+          if colorize
+            Term::ANSIColor.public_send(attribute.name, str)
+          else
+            str
+          end
+        end
+      end
+    end
+  end
+end