diff --git a/README.markdown b/README.markdown
index 94b4e9c..f8d01e1 100644
--- a/README.markdown
+++ b/README.markdown
@@ -66,6 +66,8 @@ RbbCode supports the following BBCode features:
   * [i]
   * [u]
   * [s]
+  * [size]
+  * [color]
   * [url]
   * [img]
   * [quote]
diff --git a/lib/rbbcode.rb b/lib/rbbcode.rb
index cc9849a..d00261a 100644
--- a/lib/rbbcode.rb
+++ b/lib/rbbcode.rb
@@ -25,16 +25,17 @@ def self.parser_class
     end
     RbbCodeGrammarParser
   end
-  
+
   def initialize(options = {})
     @options = {
       :output_format => :html,
       :emoticons => false,
       :sanitize => true,
+      :unsupported_features => :remove,
       :sanitize_config => RbbCode::DEFAULT_SANITIZE_CONFIG
     }.merge(options)
   end
-  
+
   def convert(bb_code, options = {})
     # Options passed to #convert will override any options passed to .new.
     options = @options.merge(options)
@@ -69,4 +70,4 @@ def convert_emoticons(output)
   def output_format
     @options[:output_format]
   end
-end
\ No newline at end of file
+end
diff --git a/lib/rbbcode/node_extensions.rb b/lib/rbbcode/node_extensions.rb
index 0498c19..041114a 100644
--- a/lib/rbbcode/node_extensions.rb
+++ b/lib/rbbcode/node_extensions.rb
@@ -5,7 +5,7 @@ def strip_quotes(str)
       str.sub(/^"+/, '').sub(/"+$/, '')
     end
   end
-  
+
   module RecursiveConversion
     def recursively_convert(node, output_method, options, depth = 0)
       if node.terminal?
@@ -34,7 +34,7 @@ def recursively_convert(node, output_method, options, depth = 0)
       end
     end
   end
-  
+
   module DocumentNode
     def to_html(options)
       contents.elements.collect { |p| p.to_html(options) }.join
@@ -44,10 +44,10 @@ def to_markdown(options)
       contents.elements.collect { |p| p.to_markdown(options) }.join
     end
   end
-  
+
   module ParagraphNode
     include RecursiveConversion
-    
+
     def to_html(options)
       # Convert all child nodes, concatenate the results,
       # and wrap the concatenated HTML in <p> tags.
@@ -66,7 +66,7 @@ def to_markdown(options)
       markdown + "\n\n"
     end
   end
-  
+
   module BlockquoteNode
     include RecursiveConversion
 
@@ -102,7 +102,7 @@ def to_markdown(options)
       end + "\n\n"
     end
   end
-  
+
   module BlockquoteLineNode
     # Returns the number of line breaks after this line. May be zero for the final
     # line, since there doesn't have to be a break before [/quote].
@@ -113,7 +113,7 @@ def post_breaks
 
   module ListNode
     include RecursiveConversion
-    
+
     def to_html(options)
       # Convert the :contents child node (defined in the .treetop file)
       # and wrap the result in <ul> tags.
@@ -127,10 +127,10 @@ def to_markdown(options)
       recursively_convert(items, :to_markdown, options) + "\n"
     end
   end
-  
+
   module ListItemNode
     include RecursiveConversion
-    
+
     def to_html(options)
       # Convert the :contents child node (defined in the .treetop file)
       # and wrap the result in <li> tags.
@@ -143,13 +143,13 @@ def to_markdown(options)
       "* " + recursively_convert(contents, :to_html, options) + "\n"
     end
   end
-  
+
   # You won't find this module in the .treetop file. Instead, it's effectively a specialization
   # of TagNode, which calls to ImgTagNode when processing an img tag. (However, one of the
   # child nodes used here, :url, is indeed defined in the .treetop file.)
   module URLTagNode
     include Attributes
-    
+
     def url_to_html(options)
       # The :url child node (defined in the .treetop file) may or may not exist,
       # depending on how the link is formatted in the BBCode source.
@@ -172,7 +172,7 @@ def url_to_markdown(options)
       end
     end
   end
-  
+
   # You won't find this module in the .treetop file. Instead, it's effectively a specialization
   # of TagNode, which calls to ImgTagNode when processing an img tag.
   module ImgTagNode
@@ -185,37 +185,93 @@ def img_to_markdown(options)
     end
   end
 
+  # You won't find this module in the .treetop file. Instead, it's effectively a specialization
+  # of TagNode, which calls to ColorTagNode when processing a color tag.
+  module ColorTagNode
+    def color_to_html(options)
+      unsupported_tag(options)
+    end
+
+    def color_to_markdown(options)
+      unsupported_tag(options)
+    end
+
+    def unsupported_tag(options)
+      if options.fetch(:unsupported_features) == :remove
+        text.text_value
+      elsif options.fetch(:unsupported_features) == :span
+        '<span class="' + color_name.text_value + '">' + text.text_value + '</span>'
+      end
+    end
+  end
+
+  # You won't find this module in the .treetop file. Instead, it's effectively a specialization
+  # of TagNode, which calls to SizeTagNode when processing a size tag.
+  module SizeTagNode
+    def size_to_html(options)
+      unsupported_tag(options)
+    end
+
+    def size_to_markdown(options)
+      unsupported_tag(options)
+    end
+
+    def unsupported_tag(options)
+      if options.fetch(:unsupported_features) == :remove
+        text.text_value
+      elsif options.fetch(:unsupported_features) == :span
+        '<span class="size' + size_value.text_value + '">' + text.text_value + '</span>'
+      end
+    end
+  end
+
   module UTagNode
     def u_to_markdown(options)
       # Underlining is unsupported in Markdown. So we just ignore [u] tags.
       inner_bbcode
     end
   end
-  
+
   module TagNode
     include RecursiveConversion
-    
+
     # For each tag name, we can either: (a) map to a simple HTML tag or Markdown character, or
     # (b) invoke a separate Ruby module for more advanced logic.
     TAG_MAPPINGS = {
-      html: {'b' => 'strong', 'i' => 'em', 'u' => 'u', 'url' => URLTagNode, 'img' => ImgTagNode},
-      markdown: {'b' => '**', 'i' => '*', 'u' => UTagNode, 'url' => URLTagNode, 'img' => ImgTagNode}
+      html: {
+        'b' => 'strong',
+        'i' => 'em',
+        'u' => 'u',
+        'url' => URLTagNode,
+        'img' => ImgTagNode,
+        'color' => ColorTagNode,
+        'size' => SizeTagNode
+      },
+      markdown: {
+        'b' => '**',
+        'i' => '*',
+        'u' => UTagNode,
+        'url' => URLTagNode,
+        'img' => ImgTagNode,
+        'color' => ColorTagNode,
+        'size' => SizeTagNode
+      }
     }
-    
+
     def contents
       # The first element is the opening tag, the second is everything inside,
       # and the third is the closing tag.
-      elements[1] 
+      elements[1]
     end
-    
+
     def tag_name
       elements.first.text_value.slice(1..-2).downcase
     end
-    
+
     def inner_bbcode
       contents.elements.collect { |e| e.text_value }.join
     end
-    
+
     def inner_html(options)
       contents.elements.collect do |node|
         recursively_convert(node, :to_html, options)
@@ -254,7 +310,7 @@ def convert(output_format, options)
         send("wrap_#{output_format}", t, options)
       end
     end
-    
+
     def to_html(options)
       convert :html, options
     end
@@ -263,7 +319,7 @@ def to_markdown(options)
       convert :markdown, options
     end
   end
-  
+
   module SingleBreakNode
     def to_html(options)
       '<br/>'
@@ -273,7 +329,7 @@ def to_markdown(options)
       "\n"
     end
   end
-  
+
   module LiteralTextNode
     def to_html(options)
       text_value
diff --git a/lib/rbbcode/rbbcode_grammar.treetop b/lib/rbbcode/rbbcode_grammar.treetop
index 818673b..f166a9d 100644
--- a/lib/rbbcode/rbbcode_grammar.treetop
+++ b/lib/rbbcode/rbbcode_grammar.treetop
@@ -92,7 +92,7 @@ grammar RbbCodeGrammar
   
   rule tag
     # Make sure that anytime you call def_tag, you add it to this list:
-    (bold / italic / underline / simple_url / complex_url / img)
+    (bold / italic / underline / simple_url / complex_url / img / color / size)
     <RbbCode::TagNode>
   end
   
@@ -101,7 +101,19 @@ grammar RbbCodeGrammar
   <%= def_tag 'underline', 'u' %>
   <%= def_tag 'simple_url', 'url' %>
   <%= def_tag 'img', 'img' %>
-  
+
+  rule size
+    '[size=' size_value:[^\]]+ ']'
+    text:(!'[/size]' .)+
+    '[/size]'
+  end
+
+  rule color
+    '[color=' color_name:[^\]]+ ']'
+    text:(!'[/color]' .)+
+    '[/color]'
+  end
+
   rule complex_url
     '[url=' url:[^\]]+ ']'
     text:(!'[/url]' .)+
diff --git a/test/unsupported_features_test.rb b/test/unsupported_features_test.rb
new file mode 100644
index 0000000..20f9a88
--- /dev/null
+++ b/test/unsupported_features_test.rb
@@ -0,0 +1,38 @@
+require File.join(File.expand_path(File.dirname(__FILE__)), 'test_helper.rb')
+
+class TestUnsupportedFeatures < Minitest::Test
+  include RbbCode::OutputAssertions
+
+  def test_remove_color_and_size_tags_to_html
+    assert_converts_to(
+      '<p>Not colored or resized but <strong>bold.</strong></p>',
+      'Not [color=red]colored[/color] or [size=3]resized[/size] but [b]bold.[/b]',
+      {}
+    )
+  end
+
+  def test_remove_color_and_size_tags_to_markdown
+    assert_converts_to(
+      "Not colored or resized but **bold.**\n\n",
+      'Not [color=red]colored[/color] or [size=3]resized[/size] but [b]bold.[/b]',
+      { output_format: :markdown }
+    )
+  end
+
+  def test_color_and_size_with_span_tags_to_html
+    assert_converts_to(
+      '<p>Not colored or resized but <strong>bold.</strong></p>',
+      'Not [color=red]colored[/color] or [size=3]resized[/size] but [b]bold.[/b]',
+      { :unsupported_features => :span }
+    )
+  end
+
+  def test_color_and_size_with_tags_to_markdown
+    assert_converts_to(
+      "Not <span class=\"red\">colored</span> or <span class=\"size3\">resized</span> but **bold.**\n\n",
+      'Not [color=red]colored[/color] or [size=3]resized[/size] but [b]bold.[/b]',
+      { :unsupported_features => :span, output_format: :markdown }
+    )
+  end
+
+end