In order to unlock this trophy you need to trade paint with all your opponents, the easiest way to do this is to grind against the side of you opponent and then go on to win the race.
The easiest race to get this is the first career event called 'New Union Race' at California -Pacific Way.
In this event there are only 5 opponents that you need to trade paint with, the race is fairly short so if you miss this the firs time you can go back and retry.
If you have already passed this event you can retry it from the Timeline.
Here is a video