Hey!
In the gridder you can hover over a textfield. Then you will see a button "class". Click it, then enter for example "blue" (without quotes).
This adds a css class to your textfield. Then in Lay Options -> Misc Options add the following CSS into both css fields for desktop and mobile:
.blue{
background-color: blue;
padding: 20px;
}
The padding value is for having some space around the text.
