The X-rite Colorchecker Passport
I just recently purchased a handy tool for getting proper colours in photos I am taking with my DSLR.
I have yet to use this piece, but from videos I have watched – I believe it will help very much.
The idea is to do a white balance and then take a picture of the 2 paned patches with each photo shoot under differing lighting and use that picture to create a profile for those conditions ( and camera and lens).
Using the profile – software will create the scientifically correct colours within your photographs.
Here is a link to a good video on how to use the Colorchecker Passport.