I found an interesting article about colour by the well known columnist Marcel Berlins in which he mentions what he thinks is the only patented colour known as IKB. For those of us less intimate with such art history details, IKB is Yves Klein's international klein blue. At present you can see that colour for yourself at the Centre Pompidou in Paris. It is not the colour that was patented, that much I am sure of. I could not locate the exact patent that may specify either the procedure or the method for preparing such colour. On the PIUG list this very issue has been discussed, and no conclusive tracking of the patent specification has been published. On espacenet I found two patents with "Yves Klein" as the inventor but these are not for IKB. Of these two, both clearly not about a colour, one patent has the publication number FR1258418 was filled in Paris on March 2, 1960 1900hrs and issued on March 6, 1961. In those days, it seems that the INPI did work rather expediently as compared to today's EPO processing times. Although I have not gone to check the actual text of the French patent law under which this patent was issued, and given that the validity of most patents is twenty years, this one too has now fallen into the public domain - that is it has expired - and anybody is now welcome to make commercial use of procedure disclosed in the original patent specification. No, the colour is not patented, the procedure was. Interestingly enough there is a CH63020 for an aniline blue colour, however this patent was issued in 1914 by the Swiss Patent Office after having been filed in 1912, and thus it seems to be rather unlikely a candidate for IKB. When Yves Klein was mixing his paints and resins in the fifties, this Swiss patent would have long been expired. Could it be that IKB is a trademark, not a patent. Does anybody know anything concrete on this IKB patent? Just a note of clarification about patents and colours. Colour and industrial property is one complex subject, fact is that the colour itself can not be patented, however there are many a patent for fabrication of pigments, synthesis of dyes and the like.