Well that all depends on what it is you are adding and where!
Here is most of the CSS that is generated within Essential for the link buttons including the hover and active one too.
#region-main form #fgroup_id_buttonar input[type="submit"],
#region-main form #fitem_id_submitbutton input[type="submit"],
#region-main form .form-buttons input[type="submit"],
#region-main form .fp-content-center form + div input[type="submit"],
#region-main form .path-admin .buttons input[type="submit"],
#region-main form div.backup-section + form input[type="submit"],
#region-main form table#form td.submit input[type="submit"] {
background-color: #006dcc;
background-image: linear-gradient(to bottom, #08c, #04c);
background-repeat: repeat-x;
border-color: rgba(0, 0, 0, 0.1) rgba(0, 0, 0, 0.1) rgba(0, 0, 0, 0.25);
color: #fff;
text-shadow: 0 -1px 0 rgba(0, 0, 0, 0.25);
}
#region-main form #fgroup_id_buttonar input.active[type="submit"],
#region-main form #fgroup_id_buttonar input.disabled[type="submit"],
#region-main form #fgroup_id_buttonar input[type="submit"]:active,
#region-main form #fgroup_id_buttonar input[type="submit"]:focus,
#region-main form #fgroup_id_buttonar input[type="submit"]:hover,
#region-main form #fgroup_id_buttonar input[type="submit"][disabled],
#region-main form #fitem_id_submitbutton input.active[type="submit"],
#region-main form #fitem_id_submitbutton input.disabled[type="submit"],
#region-main form #fitem_id_submitbutton input[type="submit"]:active,
#region-main form #fitem_id_submitbutton input[type="submit"]:focus,
#region-main form #fitem_id_submitbutton input[type="submit"]:hover,
#region-main form #fitem_id_submitbutton input[type="submit"][disabled],
#region-main form .form-buttons input.active[type="submit"],
#region-main form .form-buttons input.disabled[type="submit"],
#region-main form .form-buttons input[type="submit"]:active,
#region-main form .form-buttons input[type="submit"]:focus,
#region-main form .form-buttons input[type="submit"]:hover,
#region-main form .form-buttons input[type="submit"][disabled],
#region-main form .fp-content-center form + div input.active[type="submit"],
#region-main form .fp-content-center form + div input.disabled[type="submit"],
#region-main form .fp-content-center form + div input[type="submit"]:active,
#region-main form .fp-content-center form + div input[type="submit"]:focus,
#region-main form .fp-content-center form + div input[type="submit"]:hover,
#region-main form .fp-content-center form + div input[type="submit"][disabled],
#region-main form .path-admin .buttons input.active[type="submit"],
#region-main form .path-admin .buttons input.disabled[type="submit"],
#region-main form .path-admin .buttons input[type="submit"]:active,
#region-main form .path-admin .buttons input[type="submit"]:focus,
#region-main form .path-admin .buttons input[type="submit"]:hover,
#region-main form .path-admin .buttons input[type="submit"][disabled],
#region-main form div.backup-section + form input.active[type="submit"],
#region-main form div.backup-section + form input.disabled[type="submit"],
#region-main form div.backup-section + form input[type="submit"]:active,
#region-main form div.backup-section + form input[type="submit"]:focus,
#region-main form div.backup-section + form input[type="submit"]:hover,
#region-main form div.backup-section + form input[type="submit"][disabled],
#region-main form table#form td.submit input.active[type="submit"],
#region-main form table#form td.submit input.disabled[type="submit"],
#region-main form table#form td.submit input[type="submit"]:active,
#region-main form table#form td.submit input[type="submit"]:focus,
#region-main form table#form td.submit input[type="submit"]:hover,
#region-main form table#form td.submit input[type="submit"][disabled] {
background-color: #04c;
color: #fff;
}
#region-main form #fgroup_id_buttonar input[type="submit"] .caret,
#region-main form #fitem_id_submitbutton input[type="submit"] .caret,
#region-main form .form-buttons input[type="submit"] .caret,
#region-main form .fp-content-center form + div input[type="submit"] .caret,
#region-main form .path-admin .buttons input[type="submit"] .caret,
#region-main form div.backup-section + form input[type="submit"] .caret,
#region-main form table#form td.submit input[type="submit"] .caret {
border-bottom-color: #fff;
border-top-color: #fff;
}