Xamarin.Forms iOSでListView.PullToRefreshのインジケータの色を変える

これで替えることができました。

    internal class CustomListViewRender : ListViewRenderer
    {
        protected override void OnElementChanged(ElementChangedEventArgs<ListView> e)
        {
            base.OnElementChanged(e);
            var subview = Control?.Subviews;
            if (subview != null && subview.Any(x => x is UIRefreshControl))
            {
                var refresh = (UIRefreshControl)subview.First(x => x is UIRefreshControl);
                refresh.TintColor = UIColor.Black;
            }
        }
    }