current:
http://img238.imageshack.us/img238/8716/20090408legendcolorsmal.png

with a patch:
http://img237.imageshack.us/img237/5045/20090408legendcolorfixe.png

the patch:
===============
— zabbix-1.6.5.orig/htdocs/include/classes/chart.inc.php Wed Jun 17 17:59:12 2009
+++ zabbix-1.6.5/htdocs/include/classes/chart.inc.php Thu Jun 18 10:16:01 2009
@@ -338,7 +338,7 @@
$color = $this->GetColor('HistoryMinMax');
}
else{

• $color = $this->GetColor($this->items[$i]['color']);
  + $color = $this->GetColor($this->items[$i]['color'], GRAPH_STACKED_ALFA);
  switch($this->items[$i]['calc_fnc']){
  case CALC_FNC_MIN: $fnc_name = 'min'; break;
  case CALC_FNC_MAX: $fnc_name = 'max'; break;
  @@ -1356,10 +1356,10 @@
  else { $drawtype = $this->items[$item]['drawtype']; - $max_color = $this->GetColor('ValueMax'); - $avg_color = $this->GetColor($this->items[$item]['color']); - $min_color = $this->GetColor('ValueMin'); - $minmax_color = $this->GetColor('ValueMinMax'); + $max_color = $this->GetColor('ValueMax', GRAPH_STACKED_ALFA); + $avg_color = $this->GetColor($this->items[$item]['color'], GRAPH_STACKED_ALFA); + $min_color = $this->GetColor('ValueMin', GRAPH_STACKED_ALFA); + $minmax_color = $this->GetColor('ValueMinMax', GRAPH_STACKED_ALFA); $calc_fnc = $this->items[$item]['calc_fnc']; }

  ===============