The main trick is to be sure you check the Animatable check box BEFOREHAND, for the materials you want to affect. Then move to a new frame and change that material to the color you want; move to another frame, make another change, and so on. The result will have smooth changes of color. You can't shift from one texture image map to another, but you can change the "intensity" of the texture map, or anything else that shows up as a number or a slider on this materials panel.

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