[Tee]

You could use strcmp or:

pawn Код:

stock SendFactionMessage(playerid, color, text[])//Don't mind 'playerid'
{
    foreach(Player, i)
    {
        if(PlayerInfo[playerid][pFaction] == PlayerInfo[i][pFaction])
        {
            SendClientMessage(i, color, text);
        }
    }
    return 0;
}

Not tested but should work.