[ns] about setting the mobile node color

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Dear all
   Today, I want to set my mobile nodes to color
  
for {set i 0} {$i < $val(nn) } {incr i} {  set node_($i) [$ns_ node]   $node_($i) random-motion 0  $node_($i) color blue  $node_($i) label mobible }
 
here label "mobile" can turn up, but color is still black. what is the problom
I also changed the file "ns-lib.tcl", but problem still exist.
 
Simulator instproc initial_node_pos {nodep size} { $self instvar addressType_ $self instvar energyModel_ 
 if [info exists energyModel_] {    set nodeColor "green" } else {#  set nodeColor "black"# Added by delai to change the color for mobile nodes,use < $node color "color" >    set tempColor [$nodep set attr_(COLOR)]   if{$tempColor=="green"} {     puts "Green is reserved for nodes with energy model, you shall not set your node to green~~~"     set tempColor "black"     }   puts "Node color is set to $tempColor"   set nodeColor $tempColor }
 
please help me
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