In the seventeenth century, Newton used bis famous prism to found the physics of spectral light, thus revolutionising our thinking about colours; more than a hundred years later, Goethe protested against Newton's theory and discovered a number of new prismatic colour phenomena. Did these episodes in the history of science have any influence on the visual arts? For a decade now my visits to art museums have had an agenda: I have been looking for nineteenth-century paintings with certain spectral colour (...) (which will be described in the first half of this paper). While my search has been unsuccessful in traditional Western art, I found what I was looking for in Japa­nese art: in woodblock prints by Hokusai and Hiroshige. This is surprising; little Western science had reached Japan in their time. The second half of the paper pre­sents this riddle, which I am nowhere near solving. Even without a solution, however, a riddle can be instructive. In this case, it may help to bring into focus the fascinating exchange between two distant cultures. Much has been written on the cultural relativ­ity of colour perception, colour systematisation and colour aesthetics; I want to intro­duce a new and so far unknown case that might contribute to this debate - though the debate itself remains beyond the scope of this paper. (shrink)