You can also easily make changes to the Make an Offer button if you are familiar with css, you can add any styles to element with id "#mf_button"
Please use !important at the end of the style to override.
You can access the advanced css section by going to Setup > Look & Feel and scrolling all the way to the bottom.
We can happily make this change if you can give us access to your account and give us theme access. You can create an account over here https://help.shopify.com/manual/your-account/staff-accounts and give us only Theme access.