[Cohen]

public OnPlayerCommandText(playerid, cmdtext[])
{
if(strcmp(cmdtext, "/airportisland", true) == 0)
{
SetPlayerPos(playerid,5839.5556640625,-1724.4288330078,4.8843765258789);
SendClientMessage (playerid, 86 , "You have been teleported to the Airport.");
}
return 1;
}
return 0;
}

[Gazmull]

pawn Код:

SendClientMessage(playerid, 86, "You have been teleported to the Airport.");

this

pawn Код:

86

isn't a hex code or not defined.

you should define the number/colour or put the specific as comenzeno tried.

[KingHual]

The colors should be in hex format. Its 0xRRGGBBAA (AA is transparency)