a variable instead of a name for Tag tag in query_posts

I would like to create a page template that displays a set of posts/excerpts based on both categories and tags.
Since it is a template, I would like to use variables instead of specific values, so that I can apply it to different pages.

Here is what works using if and elseif:

$wall = 14 

Page 2
$wall = 16;

Page 3
$wall = 18

<?php query_posts('cat=$wall&tag=red+red&showposts=2&offset=1');
while (have_posts()) : the_post(); ?>
<b><a href="<?php the_permalink() ?>" rel="bookmark"><?php the_title(); ?></a></b>
<?php the_excerpt(__('Read more'));?><div style="clear:both;"></div>
<?php endwhile; ?><br />

here is what I would like to make it do

Page 1
$wall = 14
$colour = black

Page 2
$wall = 16 or 17
$colour = red

Page 3
$wall = 18 or 19 (how do I do that?)
$colour = (yellow or orange) and white (how do I do that?)
(Need help with the syntax above…)

And the code in the loop:

<?php query_posts('cat=$wall&tag=$colour&showposts=2&offset=1');
while (have_posts()) : the_post(); ?>
<b><a href="<?php the_permalink() ?>" rel="bookmark"><?php the_title(); ?></a></b>
<?php the_excerpt(__('Read more'));?><div style="clear:both;"></div>
<?php endwhile; ?><br />

Of course there is no output.
Any ideas?
Thank you in advance