Hi,
edit profile button uses bootstrap classes inherited from the template style. Anyway you can change style by adding a CSS code to your template (normally all templates allow this in configuration).
You can add a CSS code like this:

.jsn-p-opt{

    text-align:center; /* Alignment */

}

.jsn-p-opt .btn{

    color:white; /* Font color */

    background-color:blue; /* Background color */

    border-color: blue; /* Border color */

    font-size:15px; /* Font size */

    padding:10px 50px; /* The best way to set the size is to use padding */

}