Almost all colors in that template can be changed via template settings, but some of them like Bottom section of template design request to use custom CSS code.

How to change the Bottom background color 

Here is an example CSS code to change from purple (default) to green:

#sp-bottom::after {background: green;}

How to change the Bottom Image

You have two alternative methods to choose from to do this:

1. Replace that image file (use the same name & extension name) > templates/shaper_kidzy/images/bottom.png
2. But remember to change file rights after, using the FTP tool from 644 to 444.

OR

You can customize the bottom even more by overriding the image using Custom CSS

#sp-bottom::before {
  height: 275px;
  background-image: url(FULL-PATH-TO-YOUR-IMAGE-FILE);
  background-position: bottom center;
  background-repeat: no-repeat;
}

The second method requires you to know the basics of CSS, but I think as a webmaster you already know that.