two extremes.
</p>
</li></ul>

<p>The corresponding functions are <code>qualitative_hcl</code>, <code>sequential_hcl</code>,
and <code>diverging_hcl</code>. Their construction principles are explained in more detail below.
At the core is the luminance axis (i.e., light-dark contrasts):
These are easily decoded by humans and matched to high-low differences in the underlying
data. Therefore, <code>sequential_hcl</code> palettes are always based on a <em>monotonic</em>
luminance sequence whereas the colors in 