Please try to add this code in Custom css:
.content-product .button{
background-color: white;
}
.product-details font .button, .product-slide .content-product .button {
background-color: white;
border: 1px solid #CBCBCB;
}
.content-product .button:hover {
color: #000;
border: 1px solid #000;
}
.product-details .thickbox {
font-family: Assistant;
font-size: 13px;
}
.product-details span.price {
margin-top: 15px;
}
Regards