Need to use preferredColorScheme in preview. The previous code would not change the background.
struct FirstVisitAward_Previews: PreviewProvider {
static var previews: some View {
Group {
FirstVisitAward()
.frame(width:200,height:200)
.preferredColorScheme(.dark).previewDisplayName("Dark")
FirstVisitAward()
.frame(width:200, height:200)
.preferredColorScheme(.light).previewDisplayName("Light")
}
}
}