Hi
You can change the background color in “Samsara options > Custom Styles”. For Book now issue, it’s a custom issue that is not included in the support, just tell you the general solution.
1. You need to modify header.php file (Or create a child theme and copy the header.php to the child theme), add the button HTML into
<nav id="primary-menu">.....<a href="#" class="booknow">Book Now</a></nav>
2. Add your custom CSS for the button like below
.booknow{width:200px;height:80px;display:block;float:right;}
Thanks