Hello,

01. Go to Theme Settings -> Styles & Colors -> Buttons. Select the “Single buy now” element from the list and configure its colors to your needs.
https://ibb.co/Y7yhxnk

02. Please add this code to the Theme Settings > Custom CSS > Global Custom CSS:

.notifications-sticky div.wpcf7-response-output, .notifications-sticky .mc4wp-alert, .notifications-sticky :is(.woocommerce-error,.woocommerce-message,.woocommerce-info), .notifications-sticky .yith_ywraq_add_item_product_message {
	display: none;
}

Best Regards.