I mean dotted line, which is called bisettrice by the inventor command. The tubes are not convergent, there is no lateral view, where it is seen that the tubes at some point open.
If the "tubo" has been modeled as "sweep" extrusion on a path, you may be able to display the driving sketch and then change the layer in axis type.
1- view the sketch guide sweep2- carry out the boarding and, by selecting the tubes, select:3 - change the layer with the desired typeline and color 4- here is the result:Good job