[jitter] vertex ordering for segmented tunnel

Hi all, 

I'm attempting to create the wonderfull 'endless tunnel' effect in openGL. I want to do this by adding new segments in the distance, and remove them once the they moved passed the camera. 
Below is a little test setup but I'm having a few questions about it: 
- how to do the vertex ordering? Once I add a new segment (circle) things go haywire unless I use cylindrical segments, but then I can't stop thinking this is not very economical since I'd have to create the same set of vertices twice (end of segment 1 = beginning of segment two,...). This works, but seems wrong.

- I don't understand where the pink is coming from...? It seems like  the each vertex also contains color data?

- eventually this will need to be done differently, since the circle of jit.gl.gridshape also point in the middle, which gets messy when making the segments not perfectly circular.

any pointers?

#P window setfont "Sans Serif" 9.;
#P window linecount 1;
#P newex 81 61 195 196617 jit.gl.handle tunnel @inherit_transform 1;
#P newex 327 190 153 196617 jit.op @op pass pass + @val 0.2;
#P newex 23 217 66 196617 jit.multiplex;
#P newex 327 168 303 196617 jit.gl.gridshape tunnel @shape circle @matrixoutput 1 @dim 32 1;
#P window linecount 2;
#P newex 23 243 233 196617 jit.gl.mesh tunnel @draw_mode tri_strip @color 1. 1. 1. 1. @lighting_enable 0 @smooth_shading 1;
#P window linecount 1;
#P newex 23 168 303 196617 jit.gl.gridshape tunnel @shape circle @matrixoutput 1 @dim 32 1;
#P toggle 23 44 15 0;
#P newex 23 148 209 196617 jit.window tunnel @fsmenubar 0 @floating 1;
#P newex 23 80 58 196617 t b b erase;
#P newex 23 61 57 196617 qmetro 20;
#P newex 23 129 95 196617 jit.gl.render tunnel;
#P connect 7 0 9 0;
#P fasten 9 0 8 1 332 211 84 211;
#P fasten 10 0 0 0 86 108 28 108;
#P fasten 2 2 0 0 76 106 28 106;
#P connect 2 0 0 0;
#P connect 5 0 8 0;
#P connect 8 0 6 0;
#P connect 1 0 2 0;
#P connect 4 0 1 0;
#P window clipboard copycount 11;