Pulsanti con sfondo bianco

<form method="get" action="URL_PAGINA_WEB"><button class="btn success">Success</button></form>
<form method="get" action="URL_PAGINA_WEB"><button class="btn info">Info</button></form>
<form method="get" action="URL_PAGINA_WEB"><button class="btn warning">Warning</button></form>
<form method="get" action="URL_PAGINA_WEB"><button class="btn danger">Danger</button></form>
<form method="get" action="URL_PAGINA_WEB"><button class="btn default">Default</button></form>

.btn {
 border: 2px solid black;
 background-color: white;
 color: black;
 padding: 14px 28px;
 font-size: 16px;
 cursor: pointer;
}


/* Green */
.success {
 border-color: #4CAF50;
 color: green;
}

.success:hover {
 background-color: #4CAF50;
 color: white;
}

/* Blue */
.info {
 border-color: #2196F3;
 color: dodgerblue
}

.info:hover {
 background: #2196F3;
 color: white;
}

/* Orange */
.warning {
 border-color: #ff9800;
 color: orange;
}

.warning:hover {
 background: #ff9800;
 color: white;
}

/* Red */
.danger {
 border-color: #f44336;
 color: red
}

.danger:hover {
 background: #f44336;
 color: white;
}

/* Gray */
.default {
 border-color: #e7e7e7;
 color: black;
}

.default:hover {
 background: #e7e7e7;
}