Steps to reproduce:
1. Open the attached project
2. Build to iOS
3. When app opens on an iOS device, check Console log

Results: error thrown
ExecutionEngineException: Attempting to JIT compile method 'System.Collections.Generic.GenericEqualityComparer`1<UnityEngine.UI.ColorBlock>:.ctor ()' while running with --aot-only. <...>

Reproduced on: 5.5.3p3, 5.6.0f1, 2017.1.0b5 (Mono2x, iPad Mini 2, iOS 9.2.1)

THIS IS A KNOWN LIMITATION OF MONO BACKEND.

Workarounds:

• using IL2CPP instead of Mono2x Scripting backend
• Manually implement IEqualityComparer<TKey> (As described in: https://developer.xamarin.com/guides/ios/advanced_topics/limitations/#Value_types_as_Dictionary_Keys )