I had run into the similar problem recently, and managed to fix it with adding classes
body .btn-primary {
background-color: #7bc143;
border-color: #7bc143;
color: #FFF; }
body .btn-primary:hover, body .btn-primary:focus {
border-color: #6fb03a;
background-color: #6fb03a;
color: #FFF; }
body .btn-primary:active, body .btn-primary:visited, body .btn-primary:active:focus, body .btn-primary:active:hover {
border-color: #639d34;
background-color: #639d34;
color: #FFF; }
Also pay attention to [disabled] and [disabled]:hover, if this class is used on input[type=submit]. Like this:
body .btn-primary[disabled], body .btn-primary[disabled]:hover {
background-color: #7bc143;
border-color: #7bc143; }