The old, legacy (ugly) gamut warning is of little usefulness these days. Prior to Photoshop 5 and ICC color management, the idea was to have you see the out of gamut colors, then desatruate them with the sponge tool. Now that ICC profiles can do this with far greater speed and precision, plus show you the soft proof, its questionable why this is even in the application.
If it worked, it would be valuable to see where
the out-of-gamut colors are located. Anyway, here's a response I got from Pat Herold at Chromix in response to my question (posted here with his permission):
It's been known around the industry for some time that Adobe's gamut warning feature is not entirely reliable. It tends to give false positives, or in other words tends to show that colors will be in gamut which actually are not. Adobe has not updated this function through many of the recent releases of the software. I suppose they just expect it to be used for what it is: A rough approximation of what's in gamut.
The best we have been able to determine is that Adobe's system works about the same as a 2D view of the image and profile. If you look at your image and profile in ColorThink's 2D mode you might find that most of your pixels fit within the 2D boundary outline. But we know that the 3D view tells the whole story. We often find that more saturated shadows areas fall outside of the actual profile gamut in that lower area or in the extreme highlights. Is that what you are seeing?
So, the bottom line is that the ColorThink graph should be showing you more accurately what is out of gamut, and that is why you have ColorThink!