I know this question gets asked a bit but I haven’t seen a solution for the Supply theme.
All my products only have one variant that would display as default on the frontend. My current solution is to hide the variant on the frontend. But now I am wanting to sell products where a colour variant option is needed.
Does anyone have code the would hide variants with only one option Supply theme?
Rebecca 
Hii,
Welcome to the shopify community.
color variant option regarding add a custom code
Definitely we will help your for this issue, Its a time consuming task. If the theme does not have this feature. then we will implement this feature in your store with current theme. we have to check your file structure and code. you have to give us for store access.
You can directly get connected with me via email.
we can discuss there.