Fix color type string processing

sqlalchemy_utils/types/color.py

@@ -61,7 +61,7 @@ class ColorType(types.TypeDecorator, ScalarCoercible):
         self.impl = types.Unicode(max_length)
 
     def process_bind_param(self, value, dialect):
-        if value:
+        if value and isinstance(value, colour.Color):
             return six.text_type(getattr(value, self.STORE_FORMAT))
         return value
 

tests/types/test_color.py

@@ -1,3 +1,4 @@
+from flexmock import flexmock
 from pytest import mark
 import sqlalchemy as sa
 from sqlalchemy_utils import ColorType
@@ -18,6 +19,22 @@ class TestColorType(TestCase):
 
         self.Document = Document
 
+    def test_string_parameter_processing(self):
+        from colour import Color
+
+        flexmock(ColorType).should_receive('_coerce').and_return(
+            u'white'
+        )
+        document = self.Document(
+            bg_color='white'
+        )
+
+        self.session.add(document)
+        self.session.commit()
+
+        document = self.session.query(self.Document).first()
+        assert document.bg_color.hex == Color(u'white').hex
+
     def test_color_parameter_processing(self):
         from colour import Color