Orange (colour) with green, of yellow with violet ... trying to make the colours intense and not a harmony of grey". In another letter he wrote simply, "there is no orange without blue." Van Gogh, Pierre-Auguste Renoir and many other impressionist and post-impressionist painters frequently placed orange against azure or cobalt blue, to make both colours appear brighter. The actual complement of orange is azure – a colour that is one quarter of the way between blue and green on the colour spectrum. The actual complementary colour of true blue is yellow. Orange pigments are largely in the ochre or cadmium families,
The Color Orange using an orange hat, camera bag, tie, pen, paper, dress, suit, bag, etc. The Color Orange organization described it as this: "The strict censorship can ban the use of obvious symbols of human rights, but the use of The Color Orange cannot be banned." The Color Orange organization decided to paint the "Pillar of Shame" which has become a renowned memorial of the Tiananmen Massacre orange, to protest against the violation of human rights in China. The Danish artist Jens Galschiot and his staff took a flight to Hong Kong in order to paint the "Pillar of Shame" orange. As