注意：递加值不能太小，否则内存会暴涨死机。
<html>
<meta http-equiv="Content-Type" content="text/html;charset=utf-8">
<style>
span { display:inline-block; margin:5px; padding:5px; }
</style>
<body>
<script>
var d=30;
for (r=0; r<255; r+=d) {
for (g=0; g<255; g+=d) {
for (b=0; b<255; b+=d) {
var span = document.createElement('span');
var color = '#' + r.toString(16).toUpperCase().padStart(2,'0') + g.toString(16).toUpperCase().padStart(2,'0') + b.toString(16).toUpperCase().padStart(2,'0');
span.textContent = color;
span.style.backgroundColor = color;
document.body.appendChild(span);
}
}
}
</script>
</body>
</html>