left side background color css
.fullwidth {
position: relative;
width: 100%;
}
.bg-left {
background: #000;
left: 0;
top: 0;
bottom: 0;
position: absolute;
width: 50%;
}
.bg-right {
right: 0;
top: 0;
bottom: 0;
background: #ddd;
position: absolute;
width: 50%;
}