David, thanks for the site. A wealth of knowledge.
I would just like to give some feedback if I may, after reading through the entire site over a few days. I am a beginner to colour theory, so even terms like 'hue' are new to me.
I found, particularly at the beginning, some of the language to be inaccessible. I tried to unravel what you were saying a few times but eventually learned to just read on hoping it would become clearer, and it did. For example, despite the excellent Hue-Chroma-Lightness diagram fig 1.5, I did not fully understand what hue was until the Hue-Chroma-Lightness section and this sentence: 'A colour wheel represents chroma on a radial axis from the centre, and hue by position around the wheel...'. For my own understanding I translated the hue definition to 'On Fig 1.5 a single hue is the sliver of colour under the chroma line, and the level of chroma in that hue is a point on that line. The single line hue circle as depicted in fig 1.5 represents a range of hues having the same chroma.'
I can't say I understood much of the scientific stuff in the trichromacy and opponency section but more than likely I just need to read over it again.
I think you did a good job adding as many visual aids as possible, but I still would liked to have seen less text and more painting or photographic examples (more than one wouldn't hurt) to describe the phenomenon you were discussing, you are dealing with predominantly visual thinkers afterall. In particular I was disappointed by your explanation of your principles. Principles 1 and 2 I understood, and even did some experiments in photoshop to confirm, but I thought 5 to 8 were too briefly explained.
Additionally I found myself many times wishing there were some photoshop exercises I could follow along with to confirm each section of the site. Perhaps a simple sphere painting exercise in Photoshop or Painter for a lot of the sections could be devised where the reader had to translate what is learnt into a correct colour selection for any given situation?
There is certainly more to praise than criticize however. I did get a lot out of the site. As a beginner I don't think I could have a better start in my understanding of colour theory. I feel I now I have a rock solid foundation of understanding that will serve me well for ever more, so thanks again.
With regard to warm and cool colours, interior decorators use warm colours to make a large room seem smaller (make it more cosy), and they use cool colours to make small rooms seem bigger. In effect putting to use in a practical way the advancing tendency of warm colours and the receding tendency of cool colours. I find thinking of colours in this context helps me to classify whether a colour is warm or cool. For example, I once mistakenly thought a dark brown coloured rock with a blueish tinge that was sitting by a flowing river, all slicked over with water, was a cool colour, but it is not despite its context. All I had to do was imagine this colour painted on the wall of a room to realize it would make the room seem more 'cosy'. The same thinking can be used to clarify purple as a warm colour. Yellow is the colour that doesn't quite work when thinking like this however - paint a wall yellow in a room does it make the room more cosy? Perhaps its lightness and closeness to white makes it difficult to judge? There is no doubt warm and cool associations can be ambiguous.
Lastly, I submit the typos I noticed:
051 - In programs such as Painter that cleverly [simulate] the appearance and physical behaviour...
063 - Figure 6.11. Effect of adding white to opaque pigments. Unlike transparent pigments, addition of white to an opaque pigment like Cadmium Red Deep does not increase the chroma, but steadily [reduces] it.
074 - In digital painting programmes, the usual conceptual fr[a]mework for hue is the...
075 - Quinacridone Magenta, Pthalocyanine Blue (Green Shade), and any bright Lemon Yellow mix [is] about the greatest gamut...
077 - Since "warm" and "cool" are psychological associations, it is not [surprising] there is a great deal of inconsistency in usage.
082 - Figure 8.4. Chroma and colorfulness. A surface of a given chroma is more "colorful" in higher illumination (B,D) than in low illumination (A,C). [Tonal] painters would observe this difference in...
083 - Screen (RGB[)] colours have a more complex...
083 - Screen (RGB colours have a more complex geometry for a largely different reason. Among the full-chroma RGB (screen) colours... [You interchange 'screen (RGB)' and 'RGB (screen) - not consistent.]
083 - These differences [can] be accounted for by the fact that in the secondary colours, pixels of both the adjacent primaries are glowing.
083 - These differences be accounted for [because] in the secondary colours, pixels of both the adjacent primaries are glowing. [Pet hate, the use of 'the fact that' - up to you, just thought I'd highlight. Refer Strunk&White The Elements of Style pg24 ]
101 - My advice is that anyone who doesn't understand colour should not use black, but now that you've got this far you're certainly ready [to] join the black-using party...
From nothing everyday, and teach
The morning stars to sing'
-William Butler Yeats