Luckily, shadowGoogle is a Cocoa application, so modifying those items is relatively trivial (assuming you have the Developer Tools installed). Read the rest of the article for the basic how-to...
Before you start, make a copy of the shadowGoogle application in the Finder, and do all your editing on the copy. If something goes wrong, revert back to the original.
The input box and its font are stored in a file named "MainMenu.nib", which is located in Contents/Resources/English.lproj within the application's package (control-click to show the package contents). For some reason, I wasn't able to navigate to this folder in the Finder (the "Contents" folder is greyed out). However, it was easy to get to in the Terminal.
Once you've located the file, simply double-click it (if in the Finder) or type open MainMenu.nib (if in the Terminal). This should open the file with ProjectBuilder. You'll see a number of windows, but the one we're interested in is labeled "Window", and contains a blank white box at the right edge. Click once on the box so that the entire box is highlighted, and then select Tools -> Show Info (or just shift-command-I). This opens the information box for the selected text field.
In the "Colors" section of the dialog box, click on the "Text" and "Background" colors to bring up a color picker. As you set your preferred background color, you should see the box change on the screen. Feel free to change the text alignment and border style if you wish.
To change the font, select Format -> Font -> Show Fonts and select the typeface and size that you'd like to use.
Once you're done, save your changes and quit ProjectBuilder. Launch the copy of shadowGoogle and enjoy your new background color and/or font! I'm now using a nice small dark-blue Verdana 11 point font against a faint-blue background, which is much less obtrusive on my desktop.
I'm sure there are tons of other cool things that can be done with ProjectBuilder, but this hint just covered the entire breadth of my Cocoa knowledge!

