I have a class that returns a UIColor from my custom palette. I call this programmatically but when I tested it on iOS 11 it always returns a nil result... I tried
nil
This was a bug in Xcode and its fixed in the new GM Seed 2 (11A420a).
I encountered this issue as well. I was using Xcode 11 beta 6, with Command Line Tools 11.0.
I solved it by switching to Xcode 10.2.1 and Command Line Tools 10.2.1, cleaning & building again.