I picked up a really cool tip from Rui Marinho and @DhirendraKumar in answer to a forum post last month.
Suppose you want to add a view with a semi-transparent background, like this:
I personally really like this look at you can see it in many different applications.
Here is all it takes:
var slTitleBlock = new StackLayout { Padding = new Thickness(6, 5, 6, 5), BackgroundColor = new Color(0, 0, 0, 0.5), HorizontalOptions = LayoutOptions.FillAndExpand, VerticalOptions = LayoutOptions.End, Spacing = 0, Children = { lblTitle, lblSubtitle } };
Oone of the Color constructors allows you to set the Alpha Channel value, which controls the opacity of the color. By setting it to 0.5, you get the semi-transparent color.