Aperture 3 appears to use the camera’s recorded white balance information for the initial RAW preview rather than a single fixed default. Users have observed that shooting the same scene with different in-camera WB settings produces different preview renderings in Aperture, which suggests it respects the camera’s “as shot” white balance metadata.

In many RAW files, the exact WB values may be stored in maker notes or fields such as “Color Temp As Shot” or “Color Temp Auto,” not necessarily in the basic EXIF “White Balance” label alone. So the metadata field that says “Auto White Balance” may describe the mode used, while the actual chosen values can be stored elsewhere.

As for Aperture’s displayed temperature/tint values: if the White Balance adjustment is unchecked and shows placeholder values, those may not reflect the WB used for the initial preview. Based on the answers provided, Aperture does not clearly expose that initial WB choice in the default adjustment panel.

A practical way to verify behavior is to shoot the same scene with several WB settings, including a manual WB, and compare how Aperture renders each RAW preview.