Chronic ear problems can be the manifestation of food allergies. Wheat, corn and soy are the top allergens in dog foods. Dogs that are fed a grain-free diet will show immediate relief when grains are removed, if food sensitivity is the problem.
I think most of the 4 and 5 star foods are dye free. Also, there is a video that was posted today on allergies on the review side of this site under off topic discussions. It’s pretty informative. It talks a little about ear infections you might want to check it out. It’s posted by USA Dog Treats.