You will have to achieve that in css. Pls paste the following code to custom css in theme options and change the values to your liking.
.segment-class {
background: #88bfe8; /* Old browsers */
background: -moz-linear-gradient(top, #88bfe8 0%, #70b0e0 100%); /* FF3.6+ */
background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#88bfe8), color-stop(100%,#70b0e0)); /* Chrome,Safari4+ */
background: -webkit-linear-gradient(top, #88bfe8 0%,#70b0e0 100%); /* Chrome10+,Safari5.1+ */
background: -o-linear-gradient(top, #88bfe8 0%,#70b0e0 100%); /* Opera 11.10+ */
background: -ms-linear-gradient(top, #88bfe8 0%,#70b0e0 100%); /* IE10+ */
background: linear-gradient(to bottom, #88bfe8 0%,#70b0e0 100%); /* W3C */
filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#88bfe8', endColorstr='#70b0e0',GradientType=0 ); /* IE6-9 */
}
Also make sure to replace the .segment-class with the appropriate class or id. Thanks!