Ellis Vener , Feb 21, 2011; 03:13 p.m.
Iuse and rely on either of two "white" ( in reality, a light middle gray) balance targets:
The Xrite ColorChecker Passport system (also useful for calibrating a camera's color response and colro tweaking): http://www.xrite.com/product_overview.aspx?ID=1257
The WhiBal target: http://mtapesdesign.com/whibal/
The WhiBal is exceptionally color neutral (non-metameristic ( spelling?) ) under different lighting sources and in mixed/ variable light conditions.
I have tried other products. As a working professional photographer, these are the two I have come to rely on whether using Canon, Nikon, or Phase One cameras.
We all need to always be aware that that technically correct color is always expressively right (as a photographer you know that already), but both of these targets provide you with solid ground to start from.