- Explode your curves and rejoin them to create the rails for 2 rails command.
- Run sweep 2 rails command to create the blue white and red surfaces.
- Run Blendsrf command to create the violet and green surfaces
- Run Intersection commando to create a curve in the green and violet surface intersection. Probably you should edit the curve a little bit to get a clean curve.
- join the surfaces. Use showedges command and look for surfaces naked edges.