With a custom build script you have an opportunity to build a player with not compatible color space and graphics API. It means on iOS you can build Linear color space with GLES3 or GLES2 APIs and on Android Linear color space with GLES2 API.

To reproduce:
1. Open project attached by QA
2. In the menu bar select Custom Build and then select to build either for iOS or Android
3. Open the folder with project, you will find built .apk or Xcode project
4. Deploy built project to the device

Expected result: Unity shouldn't allow building project with incompatible color space and graphics API

Reproduced on: iPhone 5s iOS 9.3.3, iPhone 8+ iOS 11.0, Google Pixel 2 Adreno (TM) 540 Android 8.1.0

Reproduced with: Unity 2018.3.0b1 (trunk), 2018.1.9f2, 2018.2.2f1, 2017.3.0a1

Wasn't able to test on Desktop since it supports all APIs with every color space.