icon boxes with different background-color

Hello,
I use icon boxes on my website to structure the content. For this I use a custom css styles like a background-color, a own font- size…
But on one site, I need six different background-colors of the six icon boxes. With which code can I address the attributes that cause each Icon Box to have a different background color? In the edit function of the icon box I can not define a background color
Here is my the css code:

.iconbox_content_container {
font-size: 17px !important;
color: #4e7f22 !important;
line-height: 32px;
padding: 0.8em;
}

Thanks for help