Some small improvements

					 total        real
axlsx_noautowidth    1.650000 (  1.684738)
axlsx                4.470000 (  4.580439)
axlsx_shared         7.990000 (  8.151813)
axlsx_stream         4.420000 (  4.435809)
csv                  0.250000 (  0.259114)

1 files changed, 18 insertions, 10 deletions

diff --git a/lib/axlsx/stylesheet/color.rb b/lib/axlsx/stylesheet/color.rb
index 4e9806ad..a4942724 100644
--- a/lib/axlsx/stylesheet/color.rb
+++ b/lib/axlsx/stylesheet/color.rb
@@ -5,9 +5,9 @@ module Axlsx
     # Determines if the color is system color dependant
     # @return [Boolean]
     attr_reader :auto
-    
-    # The color as defined in rgb terms. 
-    # @note 
+
+    # The color as defined in rgb terms.
+    # @note
     #  rgb colors need to conform to ST_UnsignedIntHex. That basically means put 'FF' before you color
     # When assigning the rgb value the behavior is much like CSS selectors and can use shorthand versions as follows:
     # If you provide a two character value it will be repeated for each r, g, b assignment
@@ -25,16 +25,16 @@ module Axlsx
     # no support for theme just yet
     # @return [Integer]
     #attr_reader :theme
-    
+
     # The tint value.
     # @note valid values are between -1.0 and 1.0
     # @return [Float]
     attr_reader :tint
-    
+
     # Creates a new Color object
     # @option options [Boolean] auto
     # @option options [String] rgb
-    # @option options [Float] tint    
+    # @option options [Float] tint
     def initialize(options={})
       @rgb = "FF000000"
       options.each do |o|
@@ -42,7 +42,7 @@ module Axlsx
       end
     end
     # @see auto
-    def auto=(v) Axlsx::validate_boolean v; @auto = v end    
+    def auto=(v) Axlsx::validate_boolean v; @auto = v end
     # @see color
     def rgb=(v)
       Axlsx::validate_string(v)
@@ -56,11 +56,19 @@ module Axlsx
     def tint=(v) Axlsx::validate_float v; @tint = v end
 
     # This version does not support themes
-    # def theme=(v) Axlsx::validate_unsigned_integer v; @theme = v end    
-    
+    # def theme=(v) Axlsx::validate_unsigned_integer v; @theme = v end
+
     # Indexed colors are for backward compatability which I am choosing not to support
-    # def indexed=(v) Axlsx::validate_unsigned_integer v; @indexed = v end     
+    # def indexed=(v) Axlsx::validate_unsigned_integer v; @indexed = v end
 
+    def to_xml_string
+      str = ["<color "]
+      str << "tint='%s' " % tint if @tint
+      str << "rgb='%s' " % rgb if @rgb
+      str << "auto='%s'" % auto if @auto
+      str << "/>"
+      str.join
+    end
 
     # Serializes the color
     # @param [Nokogiri::XML::Builder] xml The document builder instance this objects xml will be added to.