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

my %myhash;

open my $fIn, '<', $ARGV[0] or die "could not open '$ARGV[0]': $!\n";

while (defined (my $line = <$fIn>)) {
    my ($word, $value) = $line =~ m/(\w+):(-?\d+)/;

    $myhash{$word} += $value;
}

while (my ($key, $value) = each %myhash) {
    print "$key: $value\n";
}

##</code><code>##

green: 311
blue: 45
red: 27
yellow: 114