Change the colours of an iframe when you don't have access to any css

iframe-container.html

    <!--[if IE]>
      <style>
      .iframe--blend{
        background-color: #fffdf3;
      }
      </style>
    <![endif]-->

    <style>
      #iframe {
        opacity: 0;
        -webkit-transition: all 300ms ease-in-out;
        -moz-transition: all 300ms ease-in-out;
        -o-transition: all 300ms ease-in-out;
        -ms-transition: all 300ms ease-in-out;
        transition: all 300ms ease-in-out;

        width: 100%;
        height: 600px;
        margin: 0 auto;
        display: block;
        max-width: 1000px;
      }

      /* Blending the iFrame into the website */
      .iframe--blend{
        padding: 30px 0 60px;

        /* Really blend it in. Might break though...*/
        /*filter:  url(#redcoat) grayscale(6%) brightness(91%) contrast(99%);*/
        -webkit-filter:  grayscale(100%) brightness(96%); /* SVG Filter doesnt work with safari */
        -moz-filter:  url("#redcoat") brightness(96%);
        filter:  url("#redcoat") brightness(96%);
      }

      /* Chrome Only fix for colouring webkit */
      @media all and (-webkit-min-device-pixel-ratio: 0) and (min-resolution: .001dpcm) {
        .iframe--blend { -webkit-filter:  url("#redcoat") brightness(96%);  }
      }
    </style>
    <!-- Svg for colour correction, remove all yellow -->
    <svg height="0">
      <defs>
        <filter id="redcoat" color-interpolation-filters="sRGB">
          <feColorMatrix in="SourceGraphic" result="BigRed" type="matrix" values="
              0 0 0 0 0
              0 0 0 0 0
              0 0 0 0 0
              4 0 -4 0 -0.5">
        <!--  R G B  A (?) -->
          </feColorMatrix>
          <feColorMatrix type="saturate" values="0" in="SourceGraphic" result="GreySource"/>
          <feComposite operator="in" in="SourceGraphic" in2="BigRed" result="RedOriginal"/>
          <feComposite operator="atop" in="RedOriginal" in2="GreySource" result="final"/>
        </filter>
      </defs>
    </svg>
  <div class="iframe--blend">
    <iframe id="iframe" src="https://drivdigital.no" frameborder="0" onload="this.style.opacity = 1"></iframe>
  </div>