Yves Klein was an influential French artist who developed a major new technique for producing artworks. He was known for the transcendental power of his blue-based monochromes, which he developed in the late 1950s. He created a shade of blue, which he called International Klein Blue (IKB); it was a particularly vivid and intense ultramarine pigment. Klein used IKB to make sculptures, paintings, objects, and performance art works.
Klein's use of the color blue had a highly symbolic and spiritual significance. He saw it as a representation of purity, eternity and the infinite, a colour that was the colour of the sky and the sea, which he referred to as 'The Void'. He described it as possessing “an appearance of successive evanescence, as if it had to suffer a continuous disappearance, to leave as its trace in a free gesture of human feeling an eternal imprint of pure fire, materialized only in its absolute immateriality." Although blue was the colour Klein was associated with, he also used black, gold and the occasional red.
Klein believed that creating art was about capturing the power of pure emotion. By utilizing blue pigment, he was able to create works of art that evoked feelings of tranquility, mystery and awe. Additionally, the ultramarine blue related to the Mediterranean shoreline, Klein's childhood home. He believed that the blue colour symbolized inner life as well as distant landscapes and nostalgia.
In conclusion, Yves Klein used blue for his art works for its transcedental, symbolic and spiritual significance. He believed that by using this colour he could convey feelings of tranquility, mystery, awe and nostalgia.
You can find out more about Yves Klein and his work here: https://www.tate.org.uk/art/artists/yves-klein-2074