I've seen this implemented before, its a steady line in the road that turns from green to red depending on how fast your going/approaching a corner. If you are going to fast it turns warmer, if your good green, on the edge yellow, etc. I think it would be a great "training" tool to get used to stopping distances and throttle control in the turns...

try this mod:
http://lfsforum.net/showthread.php?t=3322

If you really meant the mod mentioned above, then the line has nothing to do with speed.

Green means "accellerate", yellow "neutral" and red stands for "brake". This also doesn't show how it should be done but simply how your best lap was done. If your best lap is rubbish then the shown line will be rubbish too.

If you actually want to HAVE a mod where the color changes depending on your current speed, then I have to say, it would be a bit too arcadey for me. Personally I just need to watch the WR hotlap of a track once or twice and I know all the braking points

the ghost mod shows you the line and the braking points. what else do you need?

if the line tells you, you are too fast, it's too late anyways.

And the ghostmod shows your line or somebody's if you downloaded it. You would need to download it anyway for this kind of line, because who should determine what's the optimum speed? the AI? lol....