Operating system: macOS 10.14.2
Graphics card: AMD Radeon R9 M395X 4096 MB
Broken: Blender 2.8 beta Feb 4
Short description of error
The Viewport Display > Color property gets stuck when it has a keyframe. You can add one keyframe, but then it's impossible to change the color.
Exact steps for others to reproduce the error
Open the scene here:
The Viewport Display > Color (material.diffuse_color) property has a keyframe on it. Notice that you cannot change the color.
If you clear all the keyframes, it's possible to change the color again.