define some built-in rgb colors, missing fill method

source/serialization/tests/test_read.hpp

@@ -29,7 +29,7 @@ public:
         
         return wb;
     }
-    
+
     void test_read_standard_workbook()
     {
         TS_ASSERT_DIFFERS(standard_workbook(), nullptr);

source/styles/color.cpp

@@ -37,6 +37,46 @@ const color color::white()
     return color(color::type::rgb, "ffffffff");
 }
 
+const color color::red()
+{
+    return color(color::type::rgb, "ffff0000");
+}
+
+const color color::darkred()
+{
+    return color(color::type::rgb, "ff8b0000");
+}
+
+const color color::blue()
+{
+    return color(color::type::rgb, "ff0000ff");
+}
+
+const color color::darkblue()
+{
+    return color(color::type::rgb, "ff00008b");
+}
+
+const color color::green()
+{
+    return color(color::type::rgb, "ff00ff00");
+}
+
+const color color::darkgreen()
+{
+    return color(color::type::rgb, "ff008b00");
+}
+
+const color color::yellow()
+{
+    return color(color::type::rgb, "ffffff00");
+}
+
+const color color::darkyellow()
+{
+    return color(color::type::rgb, "ffcccc00");
+}
+
 color::color()
 {
 }

source/styles/fill.cpp

@@ -267,4 +267,9 @@ double fill::get_gradient_bottom() const
     return gradient_path_bottom_;
 }
 
+void fill::set_background_color(const color &c)
+{
+    background_color_ = c;
+}
+
 } // namespace xlnt