[Lynn]

This is what you're looking for.
Change the players color to transparent when he enters.
Then set it back to it's default value when he exits.

PHP код:

//Top of script
new formerColor;
// When player enters
for(new i=0;i<MAX_PLAYERS;i++)
{
    formerColor = GetPlayerColor(playerid);
    SetPlayerMarkerForPlayer(i, playerid, ( formerColor & 0xFFFFFF00 ) );
}
// When player Exits
for(new i=0;i<MAX_PLAYERS;i++)
{
    SetPlayerMarkerForPlayer(i, playerid, ( GetPlayerColor( playerid) & formerColor ) );
}