Rounded corner color and Panels background color

1. Go to sites/all/modules/panels/plugins/styles/corners/rounded_corner.inc file –

$idstr .t-edge {
  background: url($url/----(any).png) repeat-x 0 top;
font-size: 1px;
}

put any color or image you want in background. Do same with the background tags given below.

2-

$idstr .wrap-corner .l, $idstr .wrap-corner .r {
  position: absolute;
  top: 0;
  height: 11px;
  width: 11px;
  background-image: #e48f2f;
}

We can change any image in background-image: tag.

3- If we want to call any image in this file than first of all we have to paste that image in panels/plugins/styles/corners folder.