I was recently asked by a photographer as to why product photos kept having a different background colour from photo to photo even though nothing had changed in the setup other than the subject.
The answer is simple and the solution is simple.
It appears that when the photos were taken the camera was set to Auto White Balance and the camera was compensating for the changes in subject colour. If the subject was Red, the AWB would compensate and make the photo slightly cyan, like wise if the subject was blue the AWB would make the photo slightly yellow. They are opposite colours on the colour wheel.
The AWB was only doing what it was designed for. Setting AWB to manual , of the correct light type, would have helped but there are even better solutions.
Using a Neutral grey card would be the easiest solution. You can set your exposure from the card and at the same time set your better colour balance.
After the photograph is taken you then would use the White Balance tool in Photoshop or Lightroom to set your colour balance. A one click solution. Then you would copy your White Balance setting to all of the other photos to set the White Balance to all of the photos of the same product shoot.
Where do you get a Neutral Grey card?
Kodak made and sold them for years, I am not sure if they still do but there are other brands on the market. And no, just any piece of grey card will not do.
WhiBal, http://michaeltapesdesign.com/whibal.html, is an excellent product. The WhiBal cards are waterproof and hard to damage as opposed to a piece of cardboard. The website also has instructions on how to use the WhiBal.
Another White Balance solution is the ExpoDisc. http://www.expodisc.com. Watch the videos.
This attaches to your camera lens and you would place the camera at the subject position and take a photo of the lights. A bit more work but it also gives you excellent White Balance.
And last, many of the better books on Photoshop and Lightroom have a Neutral Grey card in the back of the books. The Scott Kelby books do. And the Scott Kelby books explain how to use the White Balance tool.
Even better colour control comes from making sure that you computer monitor is properly calibrated. Using a device like a Spyder is essential.
Human ability to judge colour is unreliable, your brain does too much compensating for variants in colour balance, and people have different ideas of ideal colour balance.Besides, a number of men have a genetic propensity to colour blindness. And a few women have the same issue.
High end monitors do not have the same colour display issues as less expensive monitors, but all monitors will have their colour accuracy improved or at least verified by use of a monitor calibration tool.
Your camera could also use calibrating if the need for better colour rendition is needed.
Use of a McBeth Colour Checker or X-Rite Calibration Chart http://xritephoto.com/colorchecker-targets can go a long way.
For best use, you would take a photo of the ColourChecker device with the same lighting as your subject, in the case of the product shots, you would photograph the Colour Checker at the subject position and then calibrate the resulting file through the Colour Checker software to create a profile.You would then import the profile into your Lightroom Raw and would select Develop>Camera Calibration>Profile and then select the profile you just created. This allows you to have a White Balance best calibrated for your camera and lighting conditions.
Use of the Colour Checker card also helps in establishing White and Black points in your files. This is helpful in getting and keeping the maximum tonal range of your photographs.