[Konstantinos]

pawn Code:

#if !defined isnull
    #define isnull(%1) \
                ((!(%1[0])) || (((%1[0]) == '\1') && (!(%1[1]))))
#endif

params was used, u specifier is for players' and NPCs' ID/part of name. The for loop is unnecessary.

Using ~w~ will change the color to white.

pawn Code:

dcmd_ann(playerid,params[])
{
    if(PlayerInfo[playerid][Level] < 3) return SendClientMessage(playerid,COLOR_WHITE,"{FF0000}[ERROR] {FFFFFF}You don't have an appropriate administration level to use this command.");
    if(isnull(params)) return SendClientMessage(playerid,COLOR_WHITE,""COL_ORANGE"[USAGE] {FFFFFF}/ann(ounce) [MESSAGE]");
    new message[128];
    format(message, sizeof(message), "~w~%s", params);
    GameTextForAll(message, 4000, 4 );
    return 1;
}