A: 

Try setting the "Opaque" flag to "On" for the indicator in Interface Builder.

Martin Cote
There doesn't seem to be an "Opaque" flag for the NSProgressIndicator in IB. Perhaps I'm looking in the wrong place, but I don't see one.
e.James
Every NSView has an opaque flag. It's just not settable from IB (but maybe he wasn't in front of his Mac at the time?).
Peter Hosey
OI looked up the NSView documentation. It's true that all NSView objects have that flag, but it is a read only attribute. Oh well. It looks like I'll have to use the CoreAnimation approach, or roll my own.
e.James
A: 

I've seen some third party HUD-style control frameworks that include the bar style NSProgressIndicator, but unfortunately I don't remember ever seeing the spinner. If you can't find a way to get it to do what you want, this page can generate an animated gif that might be helpful for making your own.

Marc Charbonneau
+4  A: 

Not sure if this would work correctly with NSProgressIndicator, but you might try using a Core Image filter to invert the display of the progress indicator view. You would have to make the view layer backed, and then add a CIFilter to its layer's filters. You may be able to do this all in the effects inspector in Interface Builder, otherwise you could also just do it in code.

Brian Webster
A: 

I think you want a UIActivityIndicatorView:

http://stackoverflow.com/questions/283032/background-color-for-uiactivityindicatorview

http://developer.apple.com/iphone/library/documentation/UIKit/Reference/UIActivityIndicatorView_Class/Reference/UIActivityIndicatorView.html

Sean
Sadly, UIActivityIndicator is only available in the iPhone SDK. I'm working on a desktop application.
e.James
+5  A: 

I actually have implemented clones of the spinning NSProgressIndicator that might suit your needs. They can be drawn at any size and in any color. One is a subclass of NSView, which can be used on OS X 10.4, and the other is a subclass of CALayer, which can be used in a CoreAnimation-based project. The code is on github (both the NSView-based version and the CoreAnimation-based version), and there is a post with some screenshots on my blog.

Kelan
Nice work! And here I thought this question was long dead. Thank you for the links and the code.
e.James