Representable.swift

import SwiftUI
import Combine
import SceneKit

class ViewModel: ObservableObject {
    var changeColor = PassthroughSubject<UIColor, Never>()
    var cancellables = Set<AnyCancellable>()
}

struct ContentView: View {
    @StateObject var model = ViewModel()
    
    var body: some View {
        YourView(model: model)
        
        Button("Change") {
            model.changeColor.send(UIColor.blue)
        }
    }
}

struct YourView: UIViewRepresentable {
    @ObservedObject var model: ViewModel
    
    func makeUIView(context: Context) -> SCNView {
        let view = SCNView()
        
        model.changeColor
            .sink { color in
                view.backgroundColor = color
            }
            .store(in: &model.cancellables)
        
        return view
    }
    
    func updateUIView(_ uiView: SCNView, context: Context) {}
}