change background color

You can use this CSS selector

.cat-post-pro-widget {
  background-color: #018dc2;
}

If you leave us a link or Url we can better imagine what you need.

Unfortunatelly it’s doesn’t work, CSS code is only changed text color.
You can see right side bar of this URL: https://www.kirpice.com

For me it doesn’t depends on the CSS selector. It works for me if I write it to the browser’s developer tool box:
https://www.dropbox.com/s/bmhim302tddxuxk/change%20background%20color.PNG?dl=0

So how familiar you are with writing CSS? I mean pleace write this to your Theam CSS file and clean all you caches, which you use as widget or hosting CDN.

it’s work finally. Thanks for that.

Lastly can i ask how can i add square bullet before the entry like this.

i add “list-style-type:square” code after .cat-post-title but it doesn’t work ??

https://prntscr.com/c9yq8m

This should work, see the screenshot above.

.cat-post-item {
	list-style-type: square;
	list-style-position: inside;
	margin-left: 15px;
	text-indent: -12px;
}

.cat-post-item > * {
	display: inline;
}

.cat-post-item:before, .cat-post-item:after {
	display: none !important;
}

https://www.dropbox.com/s/c9mufmvugfgkjh6/list-style%20square.PNG?dl=0

Our proposal is to create and use a Child Themes and use the styles.css file from the Child Theme. So you can update our widget and your used Theme and don’t override your custom made code.
It’s not very difficult to create and start using own Child Themes, but your advantages are huge: https://codex.www.ads-software.com/Child_Themes