How to efficiently draw jagged lines PyOpenGL?

Question

So I have some code to draw a series of parallel axes and also plot some data using these axes, the output looks something like this:

Now I have implemented this in a number of different ways to try and get the most scalable and efficient method.

All these methods work on drawing one line as a series of segments, where a segment is the line between two axes, because as far as I know OpenGL only allows the drawing of straight lines not 'jagged' ones.

1. By storing the vertices for each line segment in a Python list and using the glDraw command from here specifying 'line' as the primitive.

2. By storing the vertices for each line segment in a VBO such that the data transfer only occurs once to the GPU if I choose to re-draw the scene. Using the glDrawArrays command.

3. By storing a list of the possible axis tick locations (possible vertices for the line segments) in a VBO and then specifying an index VBO to define which ticks from the tick location VBO a line segment uses. Using the glDrawElements command.

Now the thing is the third method (indexed VBO) will not allow for different colours for different lines as the lines that share a vertex will also share the colour.

I need to establish the best method as I need to actually plot 5,000,000+ lines and my computer hangs when using method 1 or 2 for more than ~10,000 lines.

I can post some code for this if required however I am looking for an explanation as to the best method.

I am using PyOpenGL on Mac OSX 10.9 (Mavericks) and it doesn't support Primitive Restart sadly.