I have OS X 10.13.2 and Unity 2018.2.0b9 installed from Unity Hub. I imported the Raymarching Toolkit unityproject into a new empty project. During the import I got several warnings, which I did not write down. I then attempted to add a "Raymarcher" object to the project by right-clicking. Upon adding, I got the following error.
On 2017.4.6f1, I do not have any problems with the raymarch toolkit at all. If I create a working raymarch-toolkit scene in 2017.4.6f1, and import it into 2018.2.0b9, I get again an exception concerning set_colorKeys when I hit "play" and the scene does not run.
UnityException: set_colorKeys is not allowed to be called during serialization, call it from OnEnable instead. Called from ScriptableObject 'ObjectSnippet'.
See "Script Serialization" page in the Unity Manual for further details.
RaymarchingToolkit.GradientTexture.get_Default () (at <f3d48e4ad67446a5b3113996fcbb6ecb>:0)
RaymarchingToolkit.GradientTexture..ctor () (at <f3d48e4ad67446a5b3113996fcbb6ecb>:0)
UnityEngine.Resources:Load(String)
RaymarchingToolkit.RaymarchingPreferences:get_Instance()
RaymarchingToolkit.Raymarcher:get_BlitMaterial()
RaymarchingToolkit.Raymarcher:EnsureCommandBuffer(Camera)
RaymarchingToolkit.Raymarcher:OnAnyCameraPreRender(Camera)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)