Hello,
To change color of buttons, you need to use custom css code, for example, try this code:
.wishlist_table .add_to_cart.button, .btn-black, .btn.btn-black, .subscription-toggle {
background-color: red;
}
button, .button, input[type=button], input[type=submit] {
background-color: blue;
}
.btn.gray {
background-color: black;
}
You may change text for empty cart in Theme Options > Shop.
How to translate theme – https://www.8theme.com/documentation/xstore/theme-translation/base-theme-translation/ (the same for royal theme).
Regards