This example shows how color schemes can be automatically generated from configurations of hue, saturation, and luminance, displayed as vertical gradient bars across the screen. The code uses `d3.cubehelix` to define dark and light endpoints for each hue, then `d3.interpolateCubehelix` and `d3.range` to create seven-step gradients from those endpoints. It renders the resulting colors as adjacent SVG rectangles, with each rect slightly overlapping to produce seamless transitions. A CSV file provides a selected index, though the current code only reads it without affecting the visible output.