Here are some steps: 1. Go to AdminCP >> Themes >> ynclear >> Edit
2. At "Design" menu on the left, pay attention to two fields
- Header Background
- Navigation Background
3. Click "Publish" button on the top.
4. Click "Rebuild Bootstrap Core" on the same page.
5. (Important step) Clear Cache at AdminCP >> Maintenance. Note: Please always change Header Background to a certain color because darken(@brand-primary,10%) is not available on v4.4.x anymore. If you keep it and only update for others, the new style config can not save.        
February 9, 2018