fix #1521 (#1621)

templates/user/settings/email.tmpl

@@ -25,7 +25,7 @@
 												{{$.CsrfTokenHtml}}
 												<input name="_method" type="hidden" value="PRIMARY">
 												<input name="id" type="hidden" value="{{.ID}}">
-												<button class="ui green tiny button">{{$.i18n.Tr "settings.primary_email"}}</button>
+												<button class="ui blue tiny button">{{$.i18n.Tr "settings.primary_email"}}</button>
 											</form>
 										</div>
 									{{end}}