@DDD - What tricks if any? EDIT - Too bad that you didn't list the tricks or leave some hints as I'm completely stuck after dropping one ball. I'm guessing some kind of momentum move but I'm not going to sit here and wait all day for you to answer so I'm done. Moving on.
I fully agree with @ridgerunner Spoiler: Hint The first step is pretty deceptive. Getting the first step right is the only way to release R, which is essential because B and R must work as a team on several occasions to reach the win. This is a real puzzle.
@gmacpro: no tricks are required and there are no hidden elements, albeit that the final step is a bit obscure.
@GFJ - Wow - very obscure indeed as I was certain tricks were required. Thanks for the reply as the author doesn't bother to help.
@GFJ @gmacpro Can you help please? I have been looking at this one for ages and still can't see how to release R, !
@Jom yes, the first step is fairly deceptive. Spoiler: Hint It seems that the first ball should roll down, make a turn and end in the hole but this has the effect that R cannot be released. In order to avoid this situation, the ball should roll in horizontal direction until.... and B should then prevent the ball from rolling down. Good luck. It is really a true puzzle and the ball is remarkably stable.
@GFJ thanks. I'll have another go! Edit ... Aah, I've got the start now, ! Thank you. I will see where I can get from here....
Great interaction bots logic with some timing skills. Really interesting and fun. Thanks for sharing!