Copy and paste the code on your github profile page to change the graph colours... (DevTools » Console)

github-graph-colours-changer.js

// var GH = ['#EEEEEE', '#D6E685', '#8CC665', '#44A340', '#1E6823']; /* previous GH colors */
var GH = ['#EBEDF0', '#C6E48B', '#7BC96F', '#239A3B', '#196127'];
var CO = ['#EF4B4D', '#F89B47', '#FAEA20', '#7DC242', '#5D94CE', '#855CA7'];

var graph = document.getElementsByClassName('js-calendar-graph-svg')[0];
var days = [].slice.call(graph.getElementsByTagName('rect'), 0);

days.forEach(function(rect) {
    switch(rect.getAttribute('fill').toUpperCase()) {
        case GH[0]: rect.setAttribute('fill', CO[2]); break; // yellow
        case GH[1]: rect.setAttribute('fill', CO[Math.floor(Math.random() * 2)]); break; // red || orange
        case GH[2]: rect.setAttribute('fill', CO[3]); break; // green
        case GH[3]: rect.setAttribute('fill', CO[4]); break; // blue
        case GH[4]: rect.setAttribute('fill', CO[5]); break; // purple
    }
});

Nice!