<Button Text="-" TextColor="White" Padding="0" CornerRadius="4" FontAttributes="Bold" FontSize="Small" IsEnabled="False" BackgroundColor="#3F3C42" Clicked="QntLabelLess" x:Name="QntLess" Grid.Column="1" Grid.Row="1"/>

private void QntLabelLess(object sender, EventArgs e)
        {
            if (Qnt == 2)
            {
                QntLess.IsEnabled = false;
               // QntLess.TextColor = Color.FromHex("#FFFFFF");
                QntLess.BackgroundColor = Color.FromHex("#3F3C42");
            }
            if (Qnt == 10)
            {
                QntPlus.IsEnabled = true;
                QntPlus.TextColor = Color.FromHex("#000000");
                QntPlus.BackgroundColor = Color.FromHex("#FF8A00");
            }
            Qnt--;
            QntLabel.Text = Qnt.ToString();
 }