How to update a single child view in SwiftUI?

swiftui.swift

class CustomColor: BindableObject {

    var didChange = PassthroughSubject<CustomColor, Never>()

    let id = UUID()
    var color: Color {
        didSet {
            self.didChange.send(self)
        }
    }

    init(color: Color) {
        self.color = color
    }

    func change(toColor color: Color) {
        self.color = color
    }

}

class ColorStore: BindableObject {

    var didChange = PassthroughSubject<ColorStore, Never>()

    var colors: [CustomColor] = [] {
        didSet {
            didChange.send(self)
        }
    }

    init() {
        (0...10).forEach { _ in colors.append(CustomColor(color: .red)) }
    }

}


struct ContentView: View {

    @ObjectBinding var colorStore: ColorStore

    var body: some View {
        NavigationView {
            List(colorStore.colors) { color in
                ColorShape(color: color)
            }
            .navigationBarTitle(Text("Colors"))
            .navigationBarItems(trailing:
                Button(action: { self.colorStore.colors.append(CustomColor(color: .green)) }) {
                    Text("Add")
            })
        }
    }

}

struct ColorShape: View {

    @ObjectBinding var color: CustomColor

    var body: some View {
        Button(action: { self.color.change(toColor: .blue) }, label: {
            ShapeView(shape: Circle(), style: color.color)
        })
    }

}