Here's the bottom-line answer (right on top): the experts say that yes, caramel coloring is gluten-free.
There is a lot of confusion about this issue, and this answer might contradict what you have heard or read in the past. The U.S. Food and Drug Administration (F.D.A.), in its rules on color additives, says the color additive caramel can be derived from the following food-grade carbohydrates: dextrose, invert sugar, lactose, malt syrup, molasses, starch hydrolysates and fractions thereof, or sucrose. Barley malt -- which is the most common kind of malt -- would make a product off-limits to people with celiac disease.
BUT registered dietitian Shelley Case, who is on the medical advisory board of the Celiac Disease Foundation, the Gluten Intolerance Group, and the Canadian Celiac Association, told me that gluten-containing ingredients are no longer used to make caramel coloring in North America, and from my own correspondence with major manufacturers of caramel color that indeed seems to be the case. While gluten-containing ingredients can be used in the production of caramel color, North American companies are now using glucose from corn, or sometimes sucrose (table sugar). In Europe, Shelley says, companies use glucose syrup that's derived from wheat starch, but the caramel color is highly processed and contains no gluten.
Therefore, Shelley says, "Caramel color is an acceptable ingredient on the gluten-free diet and does not need to be restricted."
Code of Federal Regulations, Title 21, Volume 1, Revised as of April 1, 2009. CITE: 21CFR73.85
Shelley Case, B.Sc,RD. Gluten-Free Diet: A Comprehensive Resource Guide (Revised-Expanded Edition). Case Nutrition Consulting, Inc., Publisher. Regina, Saskatchewan, Canada, 2008.