Hi barisayarr,
Thanks for reaching to us and appreciate your patience.
1. Out of stock translation
In order to change / translate words. Please make sure you synced the strings first before changing / translating WooCommerce, WoodMart Core plugins and WoodMart theme. You can refer to article
https://xtemos.com/docs-topic/theme-translation/
2. Background color
Please add the below Custom CSS code to Theme Settings > Custom CSS > Global Custom CSS:
div.wd-product.wd-hover-base .wd-bottom-actions:not(.wd-add-small-btn) div.wd-add-btn>a:not(.ajax_add_to_cart,.add_to_cart_button){
background-color: #000;
}
Regards,