In the Version 3.0 was included in the property Spinner.DropDownTextColor.
I would suggest also adding
Spinner.DropDownBackgroundColor (simple color)
or
Spinner.DropDownBackground (drawable object)
This is necessary to prevent that "DropDownTextColor" is the same as the theme background Android in use in some devices.
I would suggest also adding
Spinner.DropDownBackgroundColor (simple color)
or
Spinner.DropDownBackground (drawable object)
This is necessary to prevent that "DropDownTextColor" is the same as the theme background Android in use in some devices.