Google Merchant Center Connected - How to add Color Gender and Age Group for Apparel

Site URL: https://www.unluckyumbrella.com/shop-art

I have some apparel products that may only come in different sizes, but one color or I don't identify the gender or age group. When these items are imported into Google Merchant Center, I have to update all the products to add this information manually.

Is there code or something I can do to the product on Squarespace to ensure I have that information so I don't need to manually update on Google Merchant center?