style.css dosyanıza şu kodları ekleyin hocam.

.pay_form form input[type="button"] {
background: #fdb515;
color: #FFFFFF;
text-align: center;
padding: 14px 0;
border: none;
font-size: 16px;
outline: none;
width: 37%;
cursor: pointer;
border-radius: 50px;
margin-bottom: 30px;
transition: 0.5s all;
-webkit-transition: 0.5s all;
-moz-transition: 0.5s all;
-o-transition: 0.5s all;
-ms-transition: 0.5s all;
}
.pay_form form input[type="button"]:hover{
background:#d24663;
transition:0.5s all;
-webkit-transition:0.5s all;
-moz-transition:0.5s all;
-o-transition:0.5s all;
-ms-transition:0.5s all;
}