I wish Bkool would drop this blue speed malarky. I am all for it to be realistic to a point, but a turbo is supposed to be harder. If I want to peddle hard or fast I don;t want the simulator deciding my speed is incompatible, Speed is what it is, Rant over
I think the blue speed down hill makes perfect sense (although I think it generally goes too fast) as it makes it realistic and allows you to have a brief rest, just like in real riding. If you want it to be harder, you can set up a proper training session (like intervals) and avoid declines, or just ride one of Bill's Goat sessions!
You can keep pedaling if you want, and if you can get a high enough cadence and a high enough gear you may actually turn the numbers white again, but the effort expended is disproportionate, again just like reality.
The blue numbers when not descending steeply, seem to be an attempt to apply some correction for limitations in the physical properties of the trainer, but they seem to be completely out of proportion for the KICKR. I think they have a lot more work to do here, and when they are as bad as they are of the start line with a KICKR, they should really remove them until they can get it right.
Away from the start line (and downhill) I guess they are applying momentum on a gradient change, but that should only be brief, as we all know that momentum is lost really quickly on the road.
Anyway, I'm all for realism as Bkool is a cycling simulator. Anyone wanting training might be better off using Trainer Road. I would say what Bkool is good at is allowing you to ride indoor, get a similar feeling to riding outdoors, experience circuits you might never get to ride (or are preparing to ride) and to interact with other riders in a way that would be very challenging (and unlikely to happen) outdoors.
Geoff