May be a reference to another resource, in the form "@[+][package:]type:name" or to a theme attribute in the form "?[package:][type:]name".

May be a color value, in the form of "#rgb", "#argb", "#rrggbb", or "#aarrggbb".

[Android Documentation]

Namespace: Android
Assembly: Mono.Android (in Mono.Android.dll)
Assembly Versions: 0.0.0.0
Since: Added in API level 1