That's not really what he means, dexter.
The P6 already comes with different paintschemes in the stock game.
But, you can't chance these during normal gameplay, sampei93.
They are selected in the mission editor when a mission is made. So if you want to sail with those, you can do it via the mission editor, make a (quick) mission, select the p6 as a playership, and then it will ask you which paintjob you want it to be.. you can of course put several in, with the different colors, etc.
You can also add more, there's user made skins floating around aswell.
Hope that answers your question. Welcome to the forums, and enjoy your stay!!
Regards,
Fred