HexClockFullSpectrum

var id = window.setTimeout(function() {}, 0);
while(id--) {
    window.clearTimeout(id);
};

var delay = 1000,  // delay in ms
    correction_24 = 255 / 24,
    correction_60 = 255 / 60;
refreshData = function() {
 	var d = new Date()
 	var h = d.getHours();
 	var m = d.getMinutes();
 	var s = d.getSeconds();
 	
 	if(h < 10) {h = '0' + h};
    if(m < 10) {m = '0' + m};
    if(s < 10) {s = '0' + s};

    hex_h = ('0' + Math.round(h * correction_24).toString(16)).slice(-2);
    hex_m = ('0' + Math.round(m * correction_60).toString(16)).slice(-2);
    hex_s = ('0' + Math.round(s * correction_60).toString(16)).slice(-2);

    var color = '#' + hex_h + hex_m + hex_s;
 	
    $("div.background").css("background-color", color);
    $("p#hex").html('#' + h + m + s + '<br><small><small><small>(really ' + color + ')</small></small></small>');

    setTimeout(refreshData, delay);
};

refreshData();

Make #HexClock (http://www.jacopocolo.com/hexclock ) go full spectrum.