MvxTextViewTextColorBinding.cs

    public class MvxTextViewTextColorBinding
        : MvxBaseAndroidTargetBinding
    {
        private readonly TextView _textView;

        public MvxTextViewTextColorBinding(TextView textView)
        {
            _textView = textView;
        }

        public override void SetValue(object value)
        {
            _textView.SetTextColor((Color)value);
        }

        public override MvxBindingMode DefaultMode
        {
            get { return MvxBindingMode.OneWay; }
        }

        public override Type TargetType
        {
            get { return typeof(Color); }
        }

    }

MvxViewBackgroundColorBinding.cs

    public class MvxViewBackgroundColorBinding
        : MvxBaseAndroidTargetBinding
    {
        private readonly View _view;

        public MvxViewBackgroundColorBinding(View view)
        {
            _view = view;
        }

        public override void SetValue(object value)
        {
            _view.SetBackgroundColor((Color)value);
        }

        public override MvxBindingMode DefaultMode
        {
            get { return MvxBindingMode.OneWay; }
        }

        public override Type TargetType
        {
            get { return typeof(Color); }
        }
    }

Setup.cs

    protected override void FillTargetFactories(Cirrious.MvvmCross.Binding.Interfaces.Bindings.Target.Construction.IMvxTargetBindingFactoryRegistry registry)
    {
      registry.RegisterFactory(new MvxCustomBindingFactory<View>("BackgroundColor", textView => new MvxViewBackgroundColorBinding(textView)));
      registry.RegisterFactory(new MvxCustomBindingFactory<TextView>("TextColor", textView => new MvxTextViewTextColorBinding(textView)));
    }