Your menus have unique identifiers based on their name, you can change them by adding these to the bottom of your theme.css.liquid file in your assets folder:
Thanks for your message and for sharing your store link.
It looks like some of our helpful community members have sent you some coding-specific help here that should get the job done. I just wanted to pop in to offer a suggestion from our end as well if you are not comfortable with manipulating your theme’s code. This may be something our Theme’s team can help you out with if you have available design time. While we’re not able to provide account-specific support via the Shopify Community at this time, we’d be happy to continue assisting you through live chat, email, or callback. If you decide to, please visit our Help center here and log in to your account to create a support request. Once you reach a live support member they will be able to check your design time as well as if our themes team can help you out with this specific customization.
So if you are not comfortable with any of the coding suggestions provided, please feel free to reach out to us directly with the steps above and we would be happy to take a look. If you are all good to go with the suggestions already provided, I hope the new changes are great and what you imagined!
Feel free to reach back out here with any questions you may have, we are always happy to chat with our merchants.