The SCLogin text color is white by default on a blue background. Your template is making the background white, which is making them merge. If you want to make the text black, add the following to your template's CSS file:
.sclogin .btn-primary {
color: #000 !important;
}Alternatively, you could remove the background color that's being applied to all buttons to make them white in your template.
I hope that helps,
Alex