This is what works for me.
Instead of adding the game as a PGN when prompted to, choose to add each individual move, and you should get a board like this one.
Making a move on this board makes it show up in the white box in the upper-right hand corner. If you click the back arrow (circled), the move will be taken back, but will remain in the white box.
If you make a move in this situation, the move will appear blue and in parenthesis: an alternative to the move that was just played.
I'm not sure about the red moves, but I know what you mean when you say that.
Hope this helped you.
How do you add variations to blog posts or in game showcase? (The text with moves that could have been made in blue or red). Thank you.