I thought I'd ask McCormick and got this reply ... I guess as far as flavor is concerned they were talking about the extracts ... it seems the color might change a little over time ...
Dear McCormick Consumer:
Thank you for taking the time to contact us. We appreciate your interest in our Assorted Food Colors and welcome the opportunity to be of assistance to you.
The McCormick Assorted Food Colors have a shelflife of 48 months from the manufacturing date. You can check the age of your spices at this link: http://www.mccormick.com/content.cfm?id=10451
The concerns about using the Assorted Food Colors beyond the "Best By" date code are flavor and/or optimum performance concerns, not health related concerns.
We invite you to join our "Friends and Flavor Club" and receive our newsletter, and personalized recipes and cooking tips. You can join by clicking on "Friends and Flavor" at www.McCormick.com.
If we can be of further assistance, please call us at 1-800-632-5847, Monday through Friday, 9:30AM to 5PM Eastern Time. If you wish to respond to this note by e-mail, please include your name and e-mail address.
We hope to have the continued pleasure of serving you.
Consumer Affairs Specialist