hr.colored {
border: 0; /* in order to override TWBS stylesheet */
height: 5px;
background: -moz-linear-gradient(left, rgba(196,222,138,1) 0%, rgba(196,222,138,1) 12.5%, rgba(245,253,212,1) 12.5%, rgba(245,253,212,1) 25%, rgba(255,208,132,1) 25%, rgba(255,208,132,1) 37.5%, rgba(242,122,107,1) 37.5%, rgba(242,122,107,1) 50%, rgba(223,157,185,1) 50%, rgba(223,157,185,1) 62.5%, rgba(192,156,221,1) 62.5%, rgba(192,156,221,1) 75%, rgba(95,156,217,1) 75%, rgba(95,156,217,1) 87.5%, rgba(94,190,227,1) 87.5%, rgba(94,190,227,1) 87.5%, rgba(94,190,227,1) 100%); /* FF3.6+ */
background: -webkit-linear-gradient(left, rgba(196,222,138,1) 0%, rgba(196,222,138,1) 12.5%, rgba(245,253,212,1) 12.5%, rgba(245,253,212,1) 25%, rgba(255,208,132,1) 25%, rgba(255,208,132,1) 37.5%, rgba(242,122,107,1) 37.5%, rgba(242,122,107,1) 50%, rgba(223,157,185,1) 50%, rgba(223,157,185,1) 62.5%, rgba(192,156,221,1) 62.5%, rgba(192,156,221,1) 75%, rgba(95,156,217,1) 75%, rgba(95,156,217,1) 87.5%, rgba(94,190,227,1) 87.5%, rgba(94,190,227,1) 87.5%, rgba(94,190,227,1) 100%); /* Chrome10+,Safari5.1+ */
background: -o-linear-gradient(left, rgba(196,222,138,1) 0%, rgba(196,222,138,1) 12.5%, rgba(245,253,212,1) 12.5%, rgba(245,253,212,1) 25%, rgba(255,208,132,1) 25%, rgba(255,208,132,1) 37.5%, rgba(242,122,107,1) 37.5%, rgba(242,122,107,1) 50%, rgba(223,157,185,1) 50%, rgba(223,157,185,1) 62.5%, rgba(192,156,221,1) 62.5%, rgba(192,156,221,1) 75%, rgba(95,156,217,1) 75%, rgba(95,156,217,1) 87.5%, rgba(94,190,227,1) 87.5%, rgba(94,190,227,1) 87.5%, rgba(94,190,227,1) 100%); /* Opera 11.10+ */
background: -ms-linear-gradient(left, rgba(196,222,138,1) 0%, rgba(196,222,138,1) 12.5%, rgba(245,253,212,1) 12.5%, rgba(245,253,212,1) 25%, rgba(255,208,132,1) 25%, rgba(255,208,132,1) 37.5%, rgba(242,122,107,1) 37.5%, rgba(242,122,107,1) 50%, rgba(223,157,185,1) 50%, rgba(223,157,185,1) 62.5%, rgba(192,156,221,1) 62.5%, rgba(192,156,221,1) 75%, rgba(95,156,217,1) 75%, rgba(95,156,217,1) 87.5%, rgba(94,190,227,1) 87.5%, rgba(94,190,227,1) 87.5%, rgba(94,190,227,1) 100%); /* IE10+ */
background: linear-gradient(to right, rgba(196,222,138,1) 0%, rgba(196,222,138,1) 12.5%, rgba(245,253,212,1) 12.5%, rgba(245,253,212,1) 25%, rgba(255,208,132,1) 25%, rgba(255,208,132,1) 37.5%, rgba(242,122,107,1) 37.5%, rgba(242,122,107,1) 50%, rgba(223,157,185,1) 50%, rgba(223,157,185,1) 62.5%, rgba(192,156,221,1) 62.5%, rgba(192,156,221,1) 75%, rgba(95,156,217,1) 75%, rgba(95,156,217,1) 87.5%, rgba(94,190,227,1) 87.5%, rgba(94,190,227,1) 87.5%, rgba(94,190,227,1) 100%); /* W3C */
}
<link href="//maxcdn.bootstrapcdn.com/bootstrap/3.3.4/css/bootstrap.min.css" rel="stylesheet"/>
<hr class="colored" />
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