You can modify the "height" parameter. Place this outside of any tags if you can.

vendor-colors-iframe.html

<div class="iframe-container">
  <iframe src="//glueboss.herokuapp.com/#/" width="1200" height="600" frameborder="0"></iframe>
</div>
<style>
  .iframe-container {
    position: relative;
    padding-bottom: 75%;
    height: 0;
    overflow: hidden;
}
.iframe-container iframe {
    position: absolute;
    top:0;
    left: 0;
    width: 100%;
    height: 100%;
    border-width: 0;
}
</style>