How can I code to grey out sold out sizes on my product page?

[daanoptroot]

Hi everyone,

I am really struggling with coding my product sizes. I want to grey out the sizes that are sold out. I got some options of other sites that are running on Shopify that have this option. Is there someone here that can help me out? 

The size of example is: https://www.kikokickz.nl/products/yeezy-350-v2-oreo?variant=42573984104665

my site is: https://keepitsneaker.com 

I really hope someone can help me out.

Thanks in advance.

Kind regards,

Daan Op 't Root

[Tinytasks]

Hi @daanoptroot 

Kindly share your store password