Add a Color class to dart:sky.

sky/engine/bindings/scripts/dart_types.py

Index: sky/engine/bindings/scripts/dart_types.py
diff --git a/sky/engine/bindings/scripts/dart_types.py b/sky/engine/bindings/scripts/dart_types.py
index 2a063b87a59b9bcdc8a8ba7c7beead79be6f7ca1..8563c222e30aebbfe9d5895bda3f882f5f7c0a44 100644
--- a/sky/engine/bindings/scripts/dart_types.py
+++ b/sky/engine/bindings/scripts/dart_types.py
@@ -114,7 +114,9 @@ CPP_SPECIAL_CONVERSION_RULES = {
     'boolean': 'bool',
     'unrestricted double': 'double',
     'unrestricted float': 'float',
-    'Rect': 'Rect',  # Pass Rect by value, not pointer.
+    # Pass these by value, not pointer.
+    'Rect': 'Rect',
+    'Color': 'CanvasColor',
 }
 
 
@@ -354,6 +356,7 @@ DART_TO_CPP_VALUE = {
     # We should handle it automatically, but map to a String for now.
     'StorageType': 'DartUtilities::dartToString(args, {index}, exception, {auto_scope})',
     'Rect': 'DartConverter<{implemented_as}>::FromArguments{null_check}(args, {index}, exception)',
+    'Color': 'DartConverter<CanvasColor>::FromArguments{null_check}(args, {index}, exception)',
 }
 
 
@@ -618,6 +621,7 @@ DART_SET_RETURN_VALUE = {
     # Typed arrays don't have special Dart* classes for Dart.
     'ArrayBuffer': 'Dart_SetReturnValue(args, DartUtilities::arrayBufferToDart({cpp_value}))',
     'TypedList': 'Dart_SetReturnValue(args, DartUtilities::arrayBufferViewToDart({cpp_value}))',
+    'Color': 'DartConverter<CanvasColor>::SetReturnValue(args, {cpp_value})',
 }