When using the basic SceneKit template, the colors will render lighter on an external pc monitor.
When running the Fox 2 scenekit wwdc demo, the colors do not have this problem.
I assume it to be a gamma multiplication, but I have searched extensively and found nothing in the code or project settings.
You can see the screenshots here: https://imgur.com/a/naGYPXO
Notice, that the statistics bar is also changed, and that it is the full rendered contents of the window that are being changed - but not the titlebar of course.
Nearly as perplexing as this: The procedural sky as viewed in the xcode scenekit interactive editor (on the internal mac display) is nearly the same as the faded lighter version on the external display. However! If the Xcode window is moved to the external display, the scenekit editor becomes even lighter.
Now, this absurdity of the scenekit editor always being lighter has been going on for years, and I am used to every modern Apple framework being bugged, and the current apple developer team being incompetent at fixing even trivial problems, however it is unclear how the first problem above exists in the scenekit project template and not the Fox 2 wwdc demo.