first of all, welcome to panda 3d.
when you paste code, feel free to use the [ code] tags. otherwise indentation will be lost(which is critical for most codes)
in panda all colors range between 0 and 1 (since panda supports more than just 8 bit colors-scales everything is managed as float values)
for your problem: you create a line, but you did not attach it to your scene-graph. so it would not show up.
[Motion path & line classes)
in this thread you can find a small class which draws lines (amongst others)
EDIT: just noticed i created lines a tad different in that thread. but you still need to wrap your line in a nodepath and reparent it to render (or some other node in the scenegraph)