Your have to chomp the variable, that is remove the trailing \n :

#!/usr/bin/perl
print "Give me a number for the tile and I will tell you the color\n";
chomp($a=<STDIN>);
print $a."\n";
%Number = qw(1 Red
    2 Yellow
    3 Green 
    4 Black 
    5 Purple 
    6 Pink 
    7 Brown 
    8 Blue 
    9 Orange);

print $Number{$a}."\n";
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BTW, your code will be cleaner if you construct your hash like this :

%Number = (1       =>    'Red',
           2       =>    'Yellow',
           3       =>    'Green');
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It'll be clearer that you are using a hash table.

On the other way you could use a array for that :

@Number = ('Red', 'Yellow', 'Green');

print $Number[$a]."\n";
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That is much more logical, as your keys are consecutive numbers. Hash a usually used when keys are strings or more complicated objects.