I was using Unity 5.1.1 and everything seems to be working fine for OpenGL 2 and 3. While updating Unity, I was reading release notes and I read default texture compression type is ETC2 for android builds now. ETC2 is only supported by OpenGL 3. I’ve build by game and tested it on OpenGL 2. Almost all textures are black. My project has over +1000 textures with individual advanced texture types. Should I do one by one for all ETC2 textures getting back to ETC1 Unity?..
This is the official answer: http://forum.unity3d.com/threads/etc2-as-default-texture-compression-on-android.348582/#post-2287082