Default Aqua Windows in OS X

[Alan Golub]

When you open a new stack window in OS X, the default mode is toplevel, and
it appears with a white background. In other modes (modeless, palette,
modal), the window gets the default Aqua background. This raises a few
questions for me:

1. What is the rational for the white background as the default in toplevel
mode? I believe that the Aqua Human Interface Guidelines suggest that all
windows get the Aqua appearance by default (with the exception of windows
that somehow connect to digital peripherals, which can get the "textured" or
"brushed metal" appearance). A look at the default window appearance in
other OS X development platforms (REALbasic, SuperCard, Apple's own
Interface Builder) confirms this.

2. Is there a way to set the appearance of a standard window to have the
Aqua background? Neither the colors nor the patterns windows appear to
include such an option for setting the background.

3. For that matter, is there a way to get the textured, or brushed metal,
appearance?

Thanks all!