Hue/Saturation Chart

Okay, so I was reading some more through Johannes Itten's The Art of Color and he had an impressive looking plate of hue/saturation (color) chart.

I've heard of people trying to replicate this chart in order to test their color skills, and when I came across it I thought "Ok, lets give this a go".

So...

I feel as though I might have done this same exercise back in my art school days. My eye has completely changed since then and I think attempting to replicate this chart with as much precision as possible is really helpful.

Here's something interesting:

I color picked my hand-painted chart in Photoshop. It was really hard to stay honest, especially since the watercolor paint that I used gave many of the squares an uneven shade and I could kind of pick from regions that helped me make the chart look more accurate then it actually was.