Yes—white balance is often available in metadata, but what you can see depends on the file type and software.

In Aperture, the white balance may be shown as an icon in the image info display. For RAW files, the White Balance adjustment can also reveal the camera’s recorded setting more precisely, including temperature/tint values.

For JPEGs, metadata is usually more limited. You may only see a basic white balance value such as Auto or Preset rather than the exact color temperature. If you need more detailed camera-recorded white balance information, RAW files generally preserve more of it than JPEGs.

For Nikon files, Nikon’s own software such as ViewNX can be useful for checking camera settings more completely. It can show basic EXIF data and, depending on the file, white balance-related settings as well.

So: Aperture may show the WB in a limited way, but for the most complete Nikon-specific white balance data, Nikon software and especially RAW files are your best bet.