Yep, I included a gray card. I included it in the front pocket of my shootsac and never took it out. Ugh. I know how to use masks now. Just can't seem to get the color right. I'll give it another pass this weekend when I'm not so tired.
Hi Sydney,
Since I don't have the original files, I did the following quick fix correction on the image you posted:
1. Opened your 'problem' image in Photoshop.
2. Create a new empty layer, and set the blending mode to Color.
3. Select that layer and choose Edit|Fill...
4. In the Fill dialog, select the Contents|Use: Color... option, and take a color sample from the wall
5. In the Fill dialog, set Blending Mode: Normal and Opacity: 100%, and select OK.
6. Invert the layer colors (Image|Adjustments|Invert)
7. Reduce the layer opacity till the wall color is neutralized (% depends on the color that was sampled), the skin looks almost normal now.
8. Create a layer mask filled with white, and reveal the original background color with painting the mask in Black. I didn't create a mask, just a quick paint brush on the mask, but a good mask would give even better results.
Based on the original files, I'm sure you will be able to do much better, and even give her a nice skin color despite the somewhat flat lighting.
The above trick also works when you e.g. shoot someone on grass or close to other dominant color reflecting/emitting surfaces. It automatically adjusts for the gradient fall-off of the color with distance.
Hope that helps.
Cheers,
Bart