I filmed a dance performance with 2 cameras (both the same model Sony Z1/FX1. One was set at indoor preset the other by accident outdoor preset. What's the best way to fix the white balance? I was thinking of filming a piece with each pre set at a white card at home to determine the color offsets between the two camera wb presets. Then apply that in FCP.

You might have a really hard time if the color shift is too extreme. First find something that is white or light grey in the bad video, crop the video until only the white is visible. Apply the 3-way Color Corrector and open the video scopes. Adjust the white color wheel until the white is in the center of the vectorscope. Clear the crop and see how the people and the blacks look. It might be close or you might need to adjust the mid levels and black color levels a bit.

Try the "match hue" in the 3 way colour corrector - takes a bit of getting used to but should fix the problem - this is for FCP 5 but will work for any version: Using Match Hue in FCP 5 (http://www.kenstone.net/fcp_homepage/match_hue_fcp_5_balis.html)

Thx I'll give the match hue a try and let you know the results.