When two wonderful books on colour swim into one's consciousness, there are many fascinating things to learn.  Surprising things, about which one has never thought and which, in fact, have shaped Western art for many centuries.

The first of the two books is Chromophilia: The Story of Color in Art by Stella Paul, who has worked at the Metropolitan Museum of Art in New York and established the Smithsonian Institution's Southern California Center for the Archives of American Art. The second book is The Secret Lives of Colour by Kassia St Clair, a freelance writer and a regular columnist for Elle Decoration.

What first stopped me in my tracks was Stella Paul's statement that even Fra Angelico, a key artist in the transition to the Renaissance in 15th century Italy, still hewed to concepts of using colour in intense, strong and integral fashion, keeping the individual pigments pure and unadulterated. He not only wanted to celebrate the wonders of beautiful pigments to echo naturalism, but also to provide a pathway to other "realities" of thought, without any degrading or "muddying" the expression by mixing the colours. This statement intrigued me.

Apparently, since antiquity, there were writings that warned against corrupting colour by mixing or using broken brush strokes, both because of the optical results of the painting but also from a philosophical point of view.  As any artist knows, the more colours you mix together, the duller and muddier the resultant colour, to say nothing of the refractive alterations and potential chemical problems. The philosophical side of the equation was far more serious for early artists and those who opined about artistic practice.  It all had to do with the ethics of mimicking nature and its creative role - yes, deep stuff! The way late medieval artists used colour was thus very much a matter of observing important traditions and strictures.

As Paul wrote, "By the first century AD, the Greek writer, Plutarch, equated the mixing of colour with moral laxity, and asserted that such stigma against blending were long-standing precepts."  Moral laxity - I wager that none of us today would ever think we might be morally lax when we select one colour over another to use in our art!  Plutarch explained his strictures against mixing hues in Moralia: "Mixing produces conflict, conflict produces change, and putrefaction is a kind of change.  This is why painters call a blending of colours 'deflowering' and Homer calls dying 'tainting' and common usage regards the unmixed as virgin and undefiled." No wonder the medieval artists still observed these moral strictures of colour purity! And it makes the ancient Greeks' belief understandable that colours ran in a continuous fashion from white to black, with yellow little darker than white, blue a little lighter than black.  Red and green were in the middle of the continuum.

Inevitably, colours took on meaning and significance in different cultures down the ages, especially given the early Western thoughts about colour and its usage. Artists were not the only ones who had to observe rules and regulations about colour.  Remember the famous restriction that one learned early in childhood about the "royal purple", the colour derived from two kinds of shellfish in the Mediterranean, Murex brandaris and Thais haemastoma, the colour that only the really powerful were allowed to wear. The earliest evidence of dyeing of purple cloth dates from the 15th century BC, especially from Tyre, where the Phoenicians grew wealthy with this skilled trade. Rome especially controlled the wearing of Tyrian purple in evermore draconian fashion, until rules relaxed under Diocletian.  Its use by the super wealthy continued until Constantinople fell to the Turks in 1453 and the secret of how to make this amazing purple dye was lost for centuries.

Ancient China, Japan and India also controlled the colours that were used and worn. A Tang dynasty(AD 618-907) edict in China, for instance, forbade "common people and officials" from wearing clothes or accessories in reddish yellow, while royal palaces sported yellow roofs and imperial ceramics often had an egg-yolk shade on their glazes.

Back in Europe, social hierarchies were increasingly delineated and separated by the use of colour.  By the mid-twelfth century, St Clair explains, "Such laws could touch on anything from diet to dress and furnishings, and sought to enforce social boundaries by encoding the social strata into a clear visual system: the peasants, in other words, should eat and dress like peasants" and so on.  Lowly peasants were restricted to dull earthy colours while bright, saturated colours like scarlet were indications of social superiority.

Only when the Renaissance began to sweep in new ideas and the older traditions were challenged did colour break out from these strictures, to expand and flower in wondrous new paintings that were not just glorious patchworks of colour but subtle depictions of all aspects of the natural world.  There was still, of course, the great philosophical argument about colour versus line or drawing. Nonetheless, as the world became more interconnected, wonderful pigments from far afield became more available, often at great expense, new techniques and materials were developed, and artists pushed out boundaries to challenge the purists who saw colour as vulgar and immoral.

Learning all about these moral outlooks on colour usage left me wondering, a little wryly, what the ancients and medieval artists would think about our use of hyper technicolour today!