How to add a block of colour / colour banner behind type in squarespace 7

Site URL: https://www.thisislandstudio.com/services

Hi there, I was wanting to add a block of colour behind the top banner in my services section.

I would like to separate the small business creative suite section from the a la carte service section.

Can I add a block of colour and have the creative suite headline and accordion sitting on top of it? 

thanks for your help

Try adding to Design > Custom CSS

div#block-yui_3_17_2_1_1647213057297_10447 h3 strong {
    background-color: black;
    color: white;
    padding-left: 10px;
    padding-right: 10px;
}