After looking at it, here is my guess: He appears to have one solid layer in the background and he placed a texture (set to "overlay") on top of that. If you make your solid very large, and then add a ramp effect to it, so that it starts as blue in one area (where your 3D camera will start) and then slowly turns to green in another area (where your camera will end up), you will get the effect that you see in the promo. The texture will appear to change from blue to green, but really it is a ramp effect applied to the solid behind the texture.
That may or may not be how he did it, but I tested this method and it works.
