How do I randomly change the color of a circle?

I'm beginning to try out SwiftUI. I want the Circle is randomly changing the color from red or green.

struct ContentView: View {
    @State var colorCircle = [".red", ".green"]

    var body: some View {
        ZStack {
            Circle()
                .fill(Color.colorCircle.randomElement())
                .frame(width: 100,
                       height: 100)
                .position(x: 250,
                          y: 320)
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}