Nice work.
When you add two custom buttons and group them, is it possible to change the color of the main button?

For example:
frm.add_custom_button(__('<i class="fa fa-google-plus" style="font-size:24px;color:blue"></i>'), function () {
frappe.msgprint("Google+");
}, __("Button"));
frm.add_custom_button(__('<i class="fa fa-print" style="font-size:24px;color:red"></i>'), function () {
frappe.msgprint("Print");
}, __("Button"));
}```