(Disclaimer: If you want to read the post as I intend it to be read, your better off opening all the spoilers first...)
I think that it was the same ball in the whole trailer.
It looks like it automatically gets brighter the faster you go, and has nothing to do with anything else.
And if you press a certain key, the ball gets red and more controlled/less bouncy, just like in WaDF.
I also believe it was the same ball, only different cores/powers that can be used at any time.
For instance, the black ball here appears to be moving full speed while on the tubes.
Though it only gets so bright.
I believe this is it's top speed for I haven't seen the black ball traveling any faster then that.
Now sure, this could easily be combated with saying it goes faster if going down hill, etc.
but I have something that says otherwise.
There is a point where the ball goes from the fast paced, high speed, white-ish blue ball to pitch black.
Now where would it have got the speed in the first pace to move that fast? That little ledge isn't that wide, and there isn't any ramps for it to roll in on.
Now, it starts darkening even though it isn't slowing down,
In the picture below the ball has hit the chain, is isn't moving forward anymore, losing all momentum.
Now at the point where it lands it suddenly picks up a large amount of speed and turns white-ish blue again.
And it repeats this again. Completely stops, then turns white/blue and hauls balls.
It the white-ish blue was simply part of the ball moving faster, none of that would have been possible.
It stands obvious to me that the white-ish blue is actually a power that speeds the ball up, or gives the ball a faster acceleration and higher top speed.
Sorry for it's length, I got just a little carried away... lol