With this Rainbow Trail the colours move through your trail while playing.
It looks pretty nice, you should give it a try!

Download: https://www.dropbox.com/s/mxd43rrmoklhgze/PRISMATIC.srt?dl=0

Installation: put .srt file here "Documents\SavedGames\SpeedRunners\CEngineStorage\AllPlayers\Trails\Local\Import"

EDIT:
If you play at more than 60 fps the trail may contain gaps. If so you have to manually reduce the life time of the particles to whatever works for you.
You could also try to increase the spawn interval, however that could leed to gaps when at max speed.
In any case, feedback is appreciated!

(On 120 fps a spawn interval of 0.015 and a life time of 1.5 seems to work pretty well)