Update Base64 SVG background image.

svgupdate.js

function updateSVG() {
    var el = document.querySelector('.icon-user');
    var style = window.getComputedStyle(el);
    var uri = style.backgroundImage;
    var svg64 = uri.replace(/^.+base64,/, "").replace(/\"?\)$/, "")
    var xml = window.atob(svg64);
    var hex = '#' + Math.floor(Math.random()*16777215).toString(16);
    var color = xml.replace(/fill="#[A-Za-z0-9]+"/, 'fill="' + hex + '"');
    var color64 = window.btoa(color);
    var colorUri = "url('data:image/svg+xml;base64," + color64 + "')";
    el.style.backgroundImage = colorUri;
}

document.querySelector('#changeme').onclick = updateSVG;