Variables de Session

[piro040815]

Buenas tardes amigos de foros del web.... estoy empezando a manejar variables de sesion y me he visto en un gran lio...
Estoy haciendo un odontograma y si sigo la secuencia de codigos que estoy haciendo terminare teniendo mas de 262 variables de sesion. se puede optimizar eso.
he aqui el codigo php

<?php
session_start();
//Recibo la Variable diagnostico: Sano / Amalgama / FX Dentaria / Caries etc.....
if(isset($_GET["diagnostico"]))
{
$diag=$_GET["diagnostico"];
}
else
{
$diag=1;
}

//Recibo la Variable odontograma: Pieza#/Pieza#-1/Pieza#-2/Pieza#-3/Pieza#-4 etc...
$_SESSION["m18"]=$_GET["m18"];
if($_SESSION["m18"]==1)
{
if($diag == 1) $_SESSION["fm18_1"]="#FFFFFF";
if($diag == 2) $_SESSION["fm18_1"]="#666666";
if($diag == 3) $_SESSION["fm18_1"]="#FF9900";
if($diag == 4) $_SESSION["fm18_1"]="#FF0000";
if($diag == 5) $_SESSION["fm18_1"]="#0000FF";
if($diag == 6) $_SESSION["fm18_1"]="#FFFF00";
if($diag == 7) $_SESSION["fm18_1"]="#00FF00";
if($diag == 8) $_SESSION["fm18_1"]="#00FFFF";
}
if($_SESSION["m18"]==2)
{
if($diag == 1) $_SESSION["fm18_2"]="#FFFFFF";
if($diag == 2) $_SESSION["fm18_2"]="#666666";
if($diag == 3) $_SESSION["fm18_2"]="#FF9900";
if($diag == 4) $_SESSION["fm18_2"]="#FF0000";
if($diag == 5) $_SESSION["fm18_2"]="#0000FF";
if($diag == 6) $_SESSION["fm18_2"]="#FFFF00";
if($diag == 7) $_SESSION["fm18_2"]="#00FF00";
if($diag == 8) $_SESSION["fm18_2"]="#00FFFF";
}
if($_SESSION["m18"]==3)
{
if($diag == 1) $_SESSION["fm18_3"]="#FFFFFF";
if($diag == 2) $_SESSION["fm18_3"]="#666666";
if($diag == 3) $_SESSION["fm18_3"]="#FF9900";
if($diag == 4) $_SESSION["fm18_3"]="#FF0000";
if($diag == 5) $_SESSION["fm18_3"]="#0000FF";
if($diag == 6) $_SESSION["fm18_3"]="#FFFF00";
if($diag == 7) $_SESSION["fm18_3"]="#00FF00";
if($diag == 8) $_SESSION["fm18_3"]="#00FFFF";
}
if($_SESSION["m18"]==4)
{
if($diag == 1) $_SESSION["fm18_4"]="#FFFFFF";
if($diag == 2) $_SESSION["fm18_4"]="#666666";
if($diag == 3) $_SESSION["fm18_4"]="#FF9900";
if($diag == 4) $_SESSION["fm18_4"]="#FF0000";
if($diag == 5) $_SESSION["fm18_4"]="#0000FF";
if($diag == 6) $_SESSION["fm18_4"]="#FFFF00";
if($diag == 7) $_SESSION["fm18_4"]="#00FF00";
if($diag == 8) $_SESSION["fm18_4"]="#00FFFF";
}
if($_SESSION["m18"]==5)
{
if($diag == 1) $_SESSION["fm18_5"]="#FFFFFF";
if($diag == 2) $_SESSION["fm18_5"]="#666666";
if($diag == 3) $_SESSION["fm18_5"]="#FF9900";
if($diag == 4) $_SESSION["fm18_5"]="#FF0000";
if($diag == 5) $_SESSION["fm18_5"]="#0000FF";
if($diag == 6) $_SESSION["fm18_5"]="#FFFF00";
if($diag == 7) $_SESSION["fm18_5"]="#00FF00";
if($diag == 8) $_SESSION["fm18_5"]="#00FFFF";
}
if($_SESSION["m18"]==6)
{
if($diag == 1)
{
unset($_SESSION["style"]);
unset($_SESSION["fm18_1"]); unset($_SESSION["fm18_2"]);
unset($_SESSION["fm18_3"]); unset($_SESSION["fm18_4"]);
unset($_SESSION["fm18_5"]);

}
if($diag == 9) $_SESSION["style"]="endodoncia";
if($diag == 10) $_SESSION["style"]="corona";
if($diag == 11) $_SESSION["style"]="ausente";
if($diag == 12) $_SESSION["style"]="implante";
if($diag == 13) $_SESSION["style"]="extraer";
if($diag == 14) $_SESSION["style"]="lcnc";
}

$_SESSION["m17"]=$_GET["m17"];
if($_SESSION["m17"]==1)
{
if($diag == 1) $_SESSION["fm17_1"]="#FFFFFF";
if($diag == 2) $_SESSION["fm17_1"]="#666666";
if($diag == 3) $_SESSION["fm17_1"]="#FF9900";
if($diag == 4) $_SESSION["fm17_1"]="#FF0000";
if($diag == 5) $_SESSION["fm17_1"]="#0000FF";
if($diag == 6) $_SESSION["fm17_1"]="#FFFF00";
if($diag == 7) $_SESSION["fm17_1"]="#00FF00";
if($diag == 8) $_SESSION["fm17_1"]="#00FFFF";
}
if($_SESSION["m17"]==2)
{
if($diag == 1) $_SESSION["fm17_2"]="#FFFFFF";
if($diag == 2) $_SESSION["fm17_2"]="#666666";
if($diag == 3) $_SESSION["fm17_2"]="#FF9900";
if($diag == 4) $_SESSION["fm17_2"]="#FF0000";
if($diag == 5) $_SESSION["fm17_2"]="#0000FF";
if($diag == 6) $_SESSION["fm17_2"]="#FFFF00";
if($diag == 7) $_SESSION["fm17_2"]="#00FF00";
if($diag == 8) $_SESSION["fm17_2"]="#00FFFF";
}
if($_SESSION["m17"]==3)
{
if($diag == 1) $_SESSION["fm17_3"]="#FFFFFF";
if($diag == 2) $_SESSION["fm17_3"]="#666666";
if($diag == 3) $_SESSION["fm17_3"]="#FF9900";
if($diag == 4) $_SESSION["fm17_3"]="#FF0000";
if($diag == 5) $_SESSION["fm17_3"]="#0000FF";
if($diag == 6) $_SESSION["fm17_3"]="#FFFF00";
if($diag == 7) $_SESSION["fm17_3"]="#00FF00";
if($diag == 8) $_SESSION["fm17_3"]="#00FFFF";
}
if($_SESSION["m17"]==4)
{
if($diag == 1) $_SESSION["fm17_4"]="#FFFFFF";
if($diag == 2) $_SESSION["fm17_4"]="#666666";
if($diag == 3) $_SESSION["fm17_4"]="#FF9900";
if($diag == 4) $_SESSION["fm17_4"]="#FF0000";
if($diag == 5) $_SESSION["fm17_4"]="#0000FF";
if($diag == 6) $_SESSION["fm17_4"]="#FFFF00";
if($diag == 7) $_SESSION["fm17_4"]="#00FF00";
if($diag == 8) $_SESSION["fm17_4"]="#00FFFF";
}
if($_SESSION["m17"]==5)
{
if($diag == 1) $_SESSION["fm17_5"]="#FFFFFF";
if($diag == 2) $_SESSION["fm17_5"]="#666666";
if($diag == 3) $_SESSION["fm17_5"]="#FF9900";
if($diag == 4) $_SESSION["fm17_5"]="#FF0000";
if($diag == 5) $_SESSION["fm17_5"]="#0000FF";
if($diag == 6) $_SESSION["fm17_5"]="#FFFF00";
if($diag == 7) $_SESSION["fm17_5"]="#00FF00";
if($diag == 8) $_SESSION["fm17_5"]="#00FFFF";
}
if($_SESSION["m17"]==6)
{
if($diag == 1)
{
unset($_SESSION["style17"]);
unset($_SESSION["fm17_1"]); unset($_SESSION["fm17_2"]);
unset($_SESSION["fm17_3"]); unset($_SESSION["fm17_4"]);
unset($_SESSION["fm17_5"]);

}
if($diag == 9) $_SESSION["style17"]="endodoncia";
if($diag == 10) $_SESSION["style17"]="corona";
if($diag == 11) $_SESSION["style17"]="ausente";
if($diag == 12) $_SESSION["style17"]="implante";
if($diag == 13) $_SESSION["style17"]="extraer";
if($diag == 14) $_SESSION["style17"]="lcnc";
}
?>

En total son 52 Piezas en la ondodoncia y cada pieza contiene 6 partes si multiplicamos esto tendria 312 variables de sesion... alguien me puede ayudar a optimizar esto.
se los voy a agradecer...