The question I have is very similar to this one, but the answer there doesn't work for me, so I'll try asking it differently here...
I switched to using raw format a while back, and am mostly happy with my ability to adjust white balance cleanly. The trouble is that I'm being forced to adjust it, every single time. When the pictures first load, I'm given the in-camera preview image, which often looks beautiful! Then Aperture's raw processing kicks in, and suddenly it turns yellow, or something equally bad happens, and I can't find an immediate way to get back to the WB of the preview image, except through painstakingly manipulating it myself, or secretly including an 18% grey item in the background.
This is with Apple Aperture 3 (v. 3.4.1, really, but it's happened for some time) and the Canon T1i. Advice welcome. I've been using their "auto-guess white balance via skin tone" tool as a quick shortcut, but it's iffy, and I'd rather not keep trying to remember to toss that 18% grey lens cloth cleaner down by the baby when taking a picture of him...