Hello Mark,
Thanks for writing to us.
The post format background color has been set from custom CSS code. You can check it in the X/Pro—>Theme option—>CSS. If you want to customize it you need to learn CSS and learn how to use the browser’s element inspector.
Here is custom CSS code that you can search in the custom CSS box.
.format-audio .entry-wrap {
color: rgb(252,242,200) !important;
background-color: rgb(225,125,74) !important;
}
.format-standard .entry-wrap {
color: rgb(255,252,221) !important;
background-color: rgb(181,186,52) !important;
}
.format-image .entry-wrap {
color: rgb(226,208,232) !important;
background-color: rgb(173,98,131) !important;
}
.format-audio .entry-wrap {
color: rgb(252,242,200) !important;
background-color: rgb(225,125,74) !important;
}
The purpose of providing the custom CSS to show you how to add CSS code to your site. Writing custom CSS is outside the scope of our theme support. If you need more customization, you need to learn CSS and learn how to use the browser’s element inspector.
Hope it helps.
Thanks