Note: Not only UI is affected. Tested and reproduced the same on: Materials, scripts with 'Color', Camera background, Lighting etc.

How to reproduce:
1. Open QA attached project
2. In hierarchy select Canvas -> Text
3. Right click on Color and select 'Copy'
4. Observe the error thrown in console

Expected behaviour: Color values copied successfully
Actual behaviour: NullReferenceException is thrown

Reproduced on: 2017.1.0b1, 2017.1.0b2
Not reproduced on: 5.6.0p3, 2017.1.0b6
Regression introduced in: 2017.1.0b1

Full error:
NullReferenceException: Object reference not set to an instance of an object
UnityEditor.EditorGUI.<DoColorField>m__5 (System.Object data, System.String[] options, Int32 selected) (at C:/buildslave/unity/build/artifacts/generated/common/editor/EditorGUIBindings.gen.cs:3793)