From looking at the pic of that bass, I would suspect that Carey used a dyed-through maple top. That is a set of maple that is dyed in such a way that the color goes all the way through. I say that as you'll notice that there is no stain on the body wood or the thin accent layer between the top and the body.
I get dyed-through maple tops from Gallery Hardwood. I haven't ordered a flamed maple top yet, just dyed through maple burl topsets. There are pics of two of them in the Gallery Hardwoods forum here on talkbass:
Blue dyed maple burl tops thread
The two tops are near the bottom, and have been dyed a blue-ish color to emulate buckeye burl.
Here is a pic of a black dyed-through maple top I also purchased from Gallery for a customers bass.
[IMG]Black http://www.gwbasses.com/projects/DanaW_DC-1/blackmaple_3.jpg[/IMG]
Not sure of the exact process by which Gallery produces these, but I know it involves a pretty elaborate vacuum chamber, and not something that could easily be done at home with a sponge brush and some wood stain.
:^)~