I believe you have two options while working on a landing page with an embedded form:
- You can change the background color of the entire form field-set by selecting the form, then clicking on the toolbox. In the window that pops up go to the second tab (it has the paint brush icon) and select the background color you would like.
- You can change the background color of the actual fields in the form by adding CSS styles. Select the toolbox, go to the very last tab (page snippet tools), and in the middle of that window you will see "Head | CSS | JS" - select that middle CSS tab and enter the style code to get the color you want. Below is an example of code you can put in there. Note that #000000 is the color code for black. Here is more info on the code: css - Background color in input and text fields? - Stack Overflow
<style type="text/css">
input, select, textarea {
background-color: #000000;
}
</style>