Outstanding collection of about 500 colour-related links on topics comprising Basic Colour Attributes, The Physical Basis of Colour, Colour Vision, Light Mixing Processes, Colorants and Colorant Mixing, Colour Order Systems, Digital Colour Technology, Colour in Art and Design, History of Colour Studies, Colour Education and Further Information.

This is the most complete online discussion of all aspects of colour science. Good explanations and illustrations, and very good discussion of many misconceptions. Not faultless but thought-inspiring. An extremely useful reference at advanced levels. 

An Artist’s Paint and Pigment Reference with Color Index Names, Color Index Numbers and Chemical Composition

The CIE International Lighting Vocabulary, first published in 1938 and revised periodically since then, gives definitions for more than 1400 terms and is by far the most comprehensive and authoritative source on the scientific terminology of light and colour. Although previously very expensive and limited in distribution, it is now freely available online.  

Outstanding webinar on the basics of human colour vision, individual differences in how we see colour, and the Implications of these individual differences for colour discrimination and colour appearance.

Overview over philosophical schools/perspectives including the phenomenological one which is of importance for our approach.

“Synaesthesia is a joining together of sensations that are normally experienced separately. Studying synaesthesia may help us to understand how the brain segregates and integrates different sensations and thoughts.” Excellent site by one of the leading research teams in synaesthesia. Site includes an up to date FAQ about synaesthesia, links to talks and references, and an online test if you think you might be a synaesthete.