under Identity Inspector as we all know that the label property is used to identify objects easier in interface builder, but what are the colors to the bottom of it used for ? I tried to select a color but nothing changed in interface builder.
EDIT: screenshot:
If you don't already use color labels to sort your files and folders, then you really should consider it. Using color labels allows you to enhance your file organization by assigning certain colors to certain files. You can assign color labels to files by doing a "Get Info" (highlight the file, then press command + i) on the file/folder and selecting a color from the label section.
What is the use of these labels if you can't search them? Well, you can! Open a new Finder window and press command + F. In the "kind" drop-down box, select "other" then find "File Label" in the list. Click it, then click "OK."
Now, you can narrow down your search by the color of its label. Note that if you are using Mac OS X Tiger, you will see "Color Label" instead of "File Label."
See the following image that help you more to understand use of identity color label..
Image when you selected first cross cube //Some file in search result
Image when you selected last(gray color) cross cube //No file in search result
Hope, this will help you..
来源：https://stackoverflow.com/questions/10379569/label-color-under-the-identity-inspector-in-xcode-4