Please change the previous code to:
.header .btn-checkout:hover {
opacity: 1 !important;
}
.header .btn-checkout, .et-wishlist-widget .wishlist-dropdown .buttons .btn-view-wishlist, .header .widget_shopping_cart .btn-view-cart {
background-color: #0b1fba !important;
color: #ffffff;
border-color: #0b1fba !important;
}
.header .btn-checkout:hover, .et-wishlist-widget .wishlist-dropdown .buttons .btn-view-wishlist:hover, .header .widget_shopping_cart .btn-view-cart:hover {
background-color: #000000 !important;
color: white;
border-color: #000000;
}
Regards