JSFiddle - React, Tailwind, and code Playground

HTML

<div class="tab">Tab1
     <div class="ribbon-wrapper-green"><div class="ribbon-green">NEW</div></div>
     </div>

CSS

.tab, .tab-active { 
    float: left; 
    position: relative;
    margin-top: 7px; 
    width: 120px; 
    height: 36px; 
    border: 2px solid #CCC; 
    border-top-left-radius: 5px; 
    border-top-right-radius: 5px; 
    border-top: none; 
    border-bottom: none; 
    background-color: #DDD; 
    text-align: center; 
    margin-right: 4px;
}

/*Ribbon*/
.ribbon-wrapper-green {
  width: 62px;
  height: 36px;
  overflow: hidden;
  position: absolute;
  top: -1px;
  right: -3px;
}

.ribbon-green {
  font: bold 9px Sans-Serif;
  color: #333;
  text-align: center;
  text-shadow: rgba(255,255,255,0.5) 0px 1px 0px;
  -webkit-transform: rotate(45deg);
  -moz-transform:    rotate(45deg);
  -ms-transform:     rotate(45deg);
  -o-transform:      rotate(45deg);
  position: relative;
  padding: 3px 0;
  left: -10px;
  top: 5px;
  width: 120px;
  background-color: #BFDC7A;
  background-image: -webkit-gradient(linear, left top, left bottom, from(#BFDC7A), to(#8EBF45)); 
  background-image: -webkit-linear-gradient(top, #BFDC7A, #8EBF45); 
  background-image:    -moz-linear-gradient(top, #BFDC7A, #8EBF45); 
  background-image:     -ms-linear-gradient(top, #BFDC7A, #8EBF45); 
  background-image:      -o-linear-gradient(top, #BFDC7A, #8EBF45); 
  color: #6a6340;
  -webkit-box-shadow: 0px 0px 3px rgba(0,0,0,0.3);
  -moz-box-shadow:    0px 0px 3px rgba(0,0,0,0.3);
  box-shadow:         0px 0px 3px rgba(0,0,0,0.3);
}

.ribbon-green:before, .ribbon-green:after {
  content: "";
  border-top:   3px solid #6e8900;   
  border-left:  3px solid transparent;
  border-right: 3px solid transparent;
  position:absolute;
  bottom: -3px;
}

.ribbon-green:before {
  left: 0;
}
.ribbon-green:after {
  right: 0;
}