How to change background page of multi-page forms

I know how to change the background page (behind the form), but multi-page forms are different lengths and the lower area retains the form colour over the whole width.

In the example screenshot I uploaded the background is dark grey on each side, but I want the bottom area to be grey as well.

Hi,

I think it has to do with the CSS code

body{

background-color: #909090;

}

I removed that code and modified the .form-all class CSS code to this instead

.form-all {

border: thin solid;

background-color: #909090 !important;

}

OK Thanks - but thats not what I wanted - you have only changed the form colour to dark grey and I want it to stay as #FFF6DE.

However you gave me the clue I wanted. 

This is what I tried and it seems to work: Change the form background to dark grey in Preferences, and body background-color to dark grey in CSS. Then override form.all background-color back to pale yellow in CSS.

.form-all {

border: thin solid;
background-color:#FFF6DE !important;
}
.form-pagebreak {
background:#F5F5F5;
}
.form-pagebreak-next-container {
padding-left: 265px;
}
.form-collapse-table {
height: 40px !important;
}
.form-collapse-mid {
font-size: 14px !important;
}
body {
background-color: #909090 !important;
}
em {color:transparent}

Thank you for input. great to see you have it working.

Do let us know if you need further assistance. Thank you.