Unity has an option to change from default Gamma Color space to Linear Color space. Changing to linear color space produces a bug that makes Unity's preview window and object inside the window very dark. This only happens with Spine objects, other preview objects such as sprites and materials show up fine.
- In Unity, go to Edit
Color Space
- Change from Gamma to Linear
(2.5. Restart Unity)
- Select a SkeletonData object in Project view
- The Preview window is very dark
