In later versions of .NET Core/.NET, you can use the generic version of Enum.GetValues like so :
var colorList = Enum.GetValues<Colors>(); //Returns an array of Color values
However in earlier versions you needed to cast the result like so :
var colorList = Enum.GetValues(typeof(Colors)).Cast<Colors>();
Either way, the static Enum helpers are the best way of getting all the possible values of an enum into a list.