Editor skin turns milky grey on importing Adam character package

Steps to Repo:
1. Create new project > Asset Store
2. Import Adam character package
https://www.assetstore.unity3d.com/en/#!/content/74842
3. Check the editor skin

Actual Result:
Editor skin color changes to milky grey

Expected Result:
Editor skin color remains same as per Unity license version

Frequency:
Always

Workaround:
Restart Unity

Environment:
Unity 2018.1.0a3

Reproducible on Windows and Mac with Unity Pro/Personal License

Working fine with Unity version 2017.3.0b7, 2017.3.0b8, 2017.2.0f3, 2017.1.2f1

Regression from 2018.a1.