@color: #FF0000;

div { height: 10px; }

div:nth-child(1) { background: darken(@color,  0%); }
div:nth-child(2) { background: darken(@color, 10%); }
div:nth-child(3) { background: darken(@color, 20%); }
div:nth-child(4) { background: darken(@color, 30%); }
div:nth-child(5) { background: darken(@color, 40%); }
div:nth-child(6) { background: darken(@color, 50%); }
