Fixing bug SDK-18188 by changing the default background color to white (FFFFFF). Legacy Flex applications can specify an override on the command line to restore the legacy grey default background color or specify a background color on the Application tag. The old default grey color was 869CA7.
QE: Yes (note that tests will need to expect a default background color of white (though I was told they have already been updated to specify white explicitly for gumbo).
Doc: Yes (we will want to add this to the compatibility/changes section).