olorfulness compared
to the corresponding gray, and luminance the brightness. This makes it relatively
easy to create balanced palettes through trajectories in this HCL space.
In contrast, in the more commonly-used <code>HSV</code> (hue-saturation-value)
model (a simple transformation of <code>RGB</code>), the three axes are
confounded so that luminance changes along with the hue leading to very
unbalanced palettes (see <code>rainbow_hcl</code> for further illustrations).
</p>
<p>Three types of palettes are