Not sure if this will actually make your code faster, as your node's title seems to imply you want, but here's a much more convenient (imho) way to store all the ranges:

#!/usr/bin/perl
use strict;
use warnings;

my @rangecolors = ( { range => [ 1e-99, 1e-90 ], color => 'orange'    
+ },
                    { range => [ 1e-90, 1e-80 ], color => 'gold'      
+ },
                    { range => [ 1e-80, 1e-70 ], color => 'yellow'    
+ },
                    { range => [ 1e-70, 1e-60 ], color => 'chartreuse'
+ },
                    { range => [ 1e-60, 1e-50 ], color => 'green'     
+ },
                    { range => [ 1e-50, 1e-40 ], color => 'turquoise' 
+ },
                    { range => [ 1e-40, 1e-30 ], color => 'navy blue' 
+ },
                    { range => [ 1e-30, 1e-20 ], color => 'lavender'  
+ },
                    { range => [ 1e-20, 1e-10 ], color => 'purple'    
+ },
                    { range => [ 1e-10, 1     ], color => 'grey'      
+ },
                  );

foreach (@rangecolors) {
    print "Between ",
          $_->{range}[0], " and ", 
          $_->{range}[1], " we want ",
          $_->{color}, "\n";
}
[download]

Note, you still need to explicitly check 0.

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