Hello,
Please add this code in Theme Options > Styling > Custom css:
.single-product .product-information-inner .out-of-stock {
background-color: transparent;
border: none;
text-align: left;
line-height: 2;
text-transform: none;
font-size: 0.9rem;
color: #e54123 !important;
padding-left: 0;
}
Regards