ok, quick and dirty way, go to BP_Sky_Sphere and change the visibility of the sky material, just to have quick access to this material from your Level blueprint.
From your Scene outliner, drag your BP_Sky_Sphere into your Level Blueprint to get a reference and here below an example of changing the zenith color, from Event Begin Play (or any Event or Trigger you want)
Result from Default Blue Sky:
On Event Begin Play:
Important nodes for dynamic material update:
All you have to know is the name of the dynamic parameters which are defined in the Material.
That said, this was an example just to show you how to quicky get results and a proper solution may be to extend the BP_Sky_Sphere and add your new functions in it, just like the updateSunDirection function. For the zenith color, take a look at the construction script and you’ll see that it rely on zenith curve and sun height parameter. You should probably take this in account when you update it so the right way tend to add your new public functionalities in the BP so you have
- access to all variables and stuff from it.
- no need to expose the sky material like in this example.