To reproduce:

1. Open Unity and create a New Project
2. Open Player settings and inspect Color Space default setting

Expected results: Color Space default setting is Gamma
Actual results: Color Space default setting is Linear

Notes:
- This issue reproduces on both Windows and OSX
- Linear Color Space is not supported on some platforms and when in the Asset Store most assets are created with Gamma premises, it creates a big mess
- That Linear Color Space is not supported on some platforms is also written in the Unity documentation:
https://docs.unity3d.com/Manual/LinearRendering-LinearOrGammaWorkflow.html

Reproduced on Unity 2018.1.0b5, 2018.1.0b13 and 2018.1.0f1
Not reproduced on Unity 2018.1.0b4 and 2018.2.0b1
Regression on Unity 2018.1.0b5