How can I change the color of unavailable sizes in my product dropdown?

[Madeleine4]

Hi, I would like to use a dropdown size picker for our products but still have the customer a) be able to immediately see which size is unavailable and b) still be able to chose that size, to then set a back in stock notification. Unfortunately the theme we are using (Combine) onle offers three options for sold out sizes: hide, show or disable. None of these works as we would need a mix of "show" and "disable", as in we want the size to show, but in a way that the customer understands its sold out (e.g. grey color) and can still click on it, to then set the notification.

Can anyone help? Thanks!

[Madeleine4]

Hi, does anyone have a clue what we could do here? Help would greatly be appreciated 🙏