Xcode Tutorial Hello World Won't Highlight

Have you checked you have imported the assets ?

I'm having the same problem, it's very annoing.

@Adam_Developer Have you checked my answer ?

problem is that tutorial is incomplete: at this step of the tutorial, come elements (themes) are missing.

Go to the end of tutorial to get the complete project. That will give you the missing elements.

Or continue the tutorial, you will reach this point for adding themes later on.