STR:
1. Open the "Repro Scene" scene in the project
2. Change the "Font Color" value in "Repro Class (script)" component on both "Normal Object" and "Prefab Object" to black
3. Save the "Repro Scene"
4. Open a new scene
5. Open "Repro Scene" again
6. Observe the "Font Color" values

Expected: "Font Color" value is retained after re-opening the scene

Actual: "Font Color" value is retained in the "Normal Object", but switched back to yellow (as it is specified in the script's initial value) in "Prefab Object"

Reproduced on: 5.3.6p8, 5.3.7f1 5.4.1p3, 5.4.1p4, 5.4.2p4, 5.5.0b11, 5.6.0a2
Not reproduced on: 5.3.6f1, 5.4.1p1, 5.4.1p2

Regression introduced in: 5.4.1p3