Reproduction steps:
1. Open the attached project.
2. Open the 'World' scene.
3. Swap between different Graphics APIs and check how the grass looks (screenshot attached).
- To swap Graphics APIs, go to File > Build Settings > Player Settings > Other Settings > Rendering and check or uncheck the Metal Editor Support checkbox.

Actual behavior:
- Colors using Metal Graphis API have less contrast than other Graphics APIs.

Reproduced with:
2017.4.0f1, 2019.2.0a6
Metal
Editor, Standalone Build

Not reproducible with:
OpenGL, DirectX