Hi,
Thanks for the screenshot.
But, please take my apology that I could not understand what to do? What you want to change? I have checked other pages and found out a black background with .8 opacity: https://prnt.sc/XasahERPQZWT. So, you want your home page component area also gets the same transparent background, right?
Then please use the following code in your custom CSS:
.homepage #sp-component-area {
background: rgba(0,0,0,0.8);
}
Hope this will serve your purpose!
Note: Path towards custom CSS(Joomla 3): Extensions>Templates>Styles> Click on your current default template name then choose Template Options. Then find custom CSS within the custom code.
Best Regards