The tutorial seems to be aimed at front-end developers that want to put together a color scheme for a website. In this case, color is more like decoration, so it doesn't need to be as rigorous, IMHO.
This is based on the architecture of human vision. When light comes into the retina, it is measured by three different types of detectors called cone cells (“long” L, “medium” M, and “short” S). But the independent signals from these cone cells are not directly passed to the visual cortex. Instead, at the first layer of processing, the cone cell responses are combined into 3 different signals, a brightness response (L + M), and two color difference signals, yellow–blue (L + M – S) and red–green (L – M). The brightness signal has the finest resolution, and is used for detection of edges, textures, fine details, motion, depth, and so on. The color difference signals are layered on top of that. “Lightness” or “value” is a perceived attribute of surface color based on the brightness response. (Caveat: this is a pretty simplified description.)
Almost any color scheme you choose which has enough lightness contrast will tend to look okay, especially if you avoid picking colors which are outrageously colorful. On the other hand, categorically, any color scheme you choose which does not have enough lightness contrast will look bad (will look muddy or clashing, text will be illegible, etc.).
Any color guide which doesn’t start with a discussion of lightness contrast is in my opinion doing a disservice to its readers.
Unfortunately, the “L” in HSL and the “V” in HSV are not remotely close to real measures of perceived lightness (value). You need to go to a different color model. The most established choice is CIELAB, from the mid-1970s, supported in a wide variety of software.
Almost any color scheme you choose which has enough
lightness contrast will tend to look okay, especially if
you avoid picking colors which are outrageously colorful.
(Ideally I would include asterisks and subscript ab in the symbols LCh to distinguish this from e.g. the cylindrical coordinates for CIELUV, but this forum doesn’t support it.)
what is it with these "experts" that think the way they see things is correct?
ever met someone with less than perfect vision... ever heard of someone with less than perfect vision?!?! this is why you have high contrast modes on your operating system, and colour blind mode in some games (not enough of this)
ffs