does anyone know why kibble vary's in color.
My guess is it's the ingredients and processing. Some poorer quality dog foods will actually add coloring to look appealing to the owners.
Veggies can change it to some degree, but I don't know how much if the food is processed, and some foods just pay lip service to that stuff in processed foods. When I add a salad mix to my dog's homemade food, it's pretty green in color, which is different than when I add beets or carrots.