Yeah, basically build a linear (whatever that means in a polar color space) gradient between two colors.

If you interpolate a bright red and bright cyan (complementary colors), the midpoint would be gray in most color spaces. You can try it in your link. But in polar color spaces (like HSLUV and most of the ones starting with H) if you just lerp each of the numbers you have to pick a direction for the hue, and your cyan—red has to pass through a saturated green, yellow or blue, magenta. That rainbow effect can be nice but doesn’t feel linear. It also creates discontinuities when you change a color stop enough.