Steps to reproduce:
1. Open project
2. Change layout to your favourite (just mine suggestion)
3. Open "Test Scene" scene
4. Go to Lighting window
5. Change Equator color to any color
-- Notice that in scene window it doesn't change
6. Change Ground color to any color
-- Notice that in scene window it doesn't change too
7. Change Sky color to any

Results: After changing sky color both ground an equator color changes takes effect although ground and equator color change is expected without sky color change.

Note: It happens despite that light baking is set to auto.

Reproduced with: 5.4.0b18; 5.3.5f1;
Not reproducible with: 5.2.4f1