Unable to apply background color for accordion

Hello Webix team,

https://snippet.webix.com/jgt47afi

In above snippet I want background color for accordion form first row not for the last row which have a button. But because of the margin I am not able to apply background color to complete row. How can I do that?

set
form padding => 0
first row padding => 10
https://snippet.webix.com/drod60h1

Thanks intregal