#!/usr/bin/perl 

use strict;
use warnings FATAL => 'all';

my @colours = (  "red", "green", "yellow", "green", "yellow", "green", "blue", "red", "green");

my %count;

$count{ $_ }++ for @colours;

print "$_\t$count{ $_ }\n" for keys %count;

__END__
output
green   4
blue    1
red     2
yellow  2