Update BoxDecoration and RenderParagraph to use sky.Color instead of int.

sky/tests/raw/render_box.dart

Index: sky/tests/raw/render_box.dart
diff --git a/sky/tests/raw/render_box.dart b/sky/tests/raw/render_box.dart
index bf44896174dd56ff6d721bd1174664aa77f25058..ceb14a4465ec8efb732451b721f225e21e504a27 100644
--- a/sky/tests/raw/render_box.dart
+++ b/sky/tests/raw/render_box.dart
@@ -14,7 +14,7 @@ void main() {
   test("should size to render view", () {
     RenderSizedBox root = new RenderSizedBox(
       child: new RenderDecoratedBox(
-        decoration: new BoxDecoration(backgroundColor: 0xFF00FF00)
+        decoration: new BoxDecoration(backgroundColor: sky.Color.green)
       )
     );
     TestView renderView = new TestView(child: root);