Hi @studiotopo
I believe all you need is to wrap the selected value within anchor tags as below.
<?php $colors = get_field('smp2'); ?>
<?php if( $colors ): ?>
<?php foreach( $colors as $color ): ?>
<a href="<?php echo link-to-the-color ?>"><span class="scolor-<?php echo $color; ?>"></span></a>
<?php endforeach;
endif; ?>
Hope this helps.