Nicely done! I played through at least seven levels and took a look at the random generator version as well. Great job fitting that all in during a game jam.
The puzzles are satisfying to solve mechanically, though all quite simple to do since you can move and adjust the ribbons easily and have extra pegs all along the outside of the board.
As you've noted, the speed of the ball is slow which is the main 'punishment' for setting things up incorrectly.
It's possible for a ribbon to be just close enough to a peg so that the color flickers on and off, I had one situation where the white I required wasn't set when I finished placing the last ball, but by touching the ball again when the ribbon was connecting, it immediately completed that level.
I also enjoyed how the levels 'built' at the start, and then reverted at the end.