First, value and lightness are synonyms in this context. The name value comes from the Munsell system, http://en.wikipedia.org/wiki/Munsell near the beginning of the 20th century, and the name lightness is what color scientists finally settled on a few decades later. Unfortunately the terms’ usage in the HSL and HSV models doesn’t have terribly much to do with the human-vision-relevant definition.

It’s too bad that the author of the linked-to post claims that chroma and saturation mean the same thing though. They don’t.

Anyhow, thanks, I’m glad you liked the pictures (I drew many of them). If there’s anything about that HSL/HSV article that could use improvement, feel free to comment here or send me an email (or you could of course leave a message on the wiki talk page).

For what it’s worth, I don’t think HSL is very intuitive. It’s basically the same thing as RGB, just tilted on one end and squished a bit into a cylinder shape (as shown here e.g., http://en.wikipedia.org/wiki/File:Hsl-and-hsv.svg). For some discussion of why, see http://en.wikipedia.org/wiki/HSL_and_HSV#Disadvantages but the short explanation is: HSL is a model designed for the hardware limitations of 1970s workstations, and much more perceptually relevant models are computationally cheap enough today.