Shopify size variant label in collection page under product.

sizevariant

<ul class="sizelist"> 
{% for option in product.options %}
{% if option == 'Size' %}
{% assign index = forloop.index0 %}
{% assign colorlist = '' %}
{% assign color = '' %}
{% for variant in product.variants %}
{% capture color %}
{{ variant.options[index] }}
{% endcapture %}

{% unless colorlist contains color %}
  {% if variant.available %}
  
  <li id="{{ variant.id }}" title="{{ variant.inventory_quantity }} In Stock" class="avactive"><a href="{{ product.url | within: collection }}?variant={{ variant.id }}">{{ color | downcase }}</a></li>
  
  {% else %}
  
  <li id="{{ variant.id }}" title="Out of Stock"  class="notactve" >{{ color | downcase }}</li>
  
  {% endif %}
  
{% capture tempList %}
{{colorlist | append: color | append: " " }}
{% endcapture %}
{% assign colorlist = tempList %}
{% endunless %}
{% endfor %}
{% endif %}
{% endfor %}
</ul>