New Skins and so-called Mods are not transmitted via online gaming. If your friends are to see those flashing nav lights, each of them has to install this Mod on his own computer.
About the skins: The information, which skin a player has selected, is transmitted (name of the skin) between players, however if this skin was replaced by a modified or new one (still using the same name), it only will show up correctly on a computer, where this specific skin was installed before. Otherwise one will see the standard Lock-On skin that comes with the game.